华盛顿——周日，一些航空公司取消了飞往乌克兰首都的航班，那里的军队从北约成员国卸下了新的武器，因为面对美国警告越来越多的俄罗斯军队可能在几天内入侵，乌克兰总统试图表现出信心。

助手们随后表示，总统沃洛季米尔·泽伦斯基(Volodymyr Zelenskyy)与总统乔·拜登(Joe Biden)交谈了大约一个小时，坚称乌克兰人对俄罗斯强大得多的军队可能发动的袭击有“安全可靠的保护”。白宫表示，双方同意继续推进威慑和外交努力，以避免令人担忧的俄罗斯军事进攻。

拜登政府越来越直言不讳地表示，它担心俄罗斯将在未来几天发动一场事件，为入侵乌克兰制造一个虚假的借口。

据两名知情人士透露，美国和欧洲情报部门最近几天的调查结果引发了人们的担忧，即俄罗斯可能会试图针对定于周二在乌克兰东部举行的乌克兰军事演习发起这种“假旗行动”。他们要求匿名，因为他们没有被授权公开谈论此事。

美国情报官员认为，将军事演习作为目标只是俄罗斯权衡假旗行动可能性的多种选择之一。白宫强调，他们不确定弗拉基米尔·普京总统是否已经做出发动入侵的最终决定。

克里姆林宫坚称，俄罗斯军队正在乌克兰北部、东部和南部集结进行军事演习。

一名美国官员更新了拜登政府的估计，即目前有多少俄罗斯军队在乌克兰边境附近集结到13万多人，高于美国前几周公开引用的10万多人。这位不愿透露姓名的官员谈到了政府的结论。

泽伦斯基一再淡化美国的警告，质疑美国官员最近几天越来越尖锐的说法，即俄罗斯可能计划最早在周中入侵。

“我们理解所有的风险，我们理解存在风险，”他在周六的一次广播中说。“如果您或任何其他人有关于16日开始的100%俄罗斯入侵的额外信息，请将该信息转发给我们。”

但是，尽管泽伦斯基敦促人们不要恐慌，他担心这可能会破坏乌克兰的经济，但他和他的文职和军事领导人也在准备防御，从美国和其他北约成员国那里寻求和接收武器。

一架载有来自北约成员国立陶宛的美国制造的“毒刺”防空导弹和弹药的军用货机周日降落，增强了该国抵御任何空中攻击的能力。

本周末，在乌克兰与被俄罗斯吞并的克里米亚接壤的边境附近，泽伦斯基穿着橄榄色军装，参加了一场坦克和直升机演习。在附近的城市卡兰查克，一些人表示不相信普京真的会派遣军队进入该国。

“我不相信俄罗斯会攻击我们，”居民鲍里斯·切雷彭科说。“我在克拉斯诺达尔的库页岛有朋友，”他说，并提到了俄罗斯的一些地区。“我不信。”

在基辅，其他人表示不确定俄罗斯的任何举动是经济上的、军事上的，还是根本不会发生。一位名叫阿洛娜·布兹尼茨卡亚的妇女在首都的一条中央街道上发表讲话，她说自己很平静，这条街道上有几个牌子，上面写着“我爱乌克兰”。

“你应该随时准备好一切，然后你就没有什么好害怕的了，”她说。

美国基本上没有公开它所说的关于俄罗斯可能的计划或时机的最具体警告背后的证据。

美国国家安全顾问杰克·沙利文(Jake Sullivan)周日对美国有线电视新闻网(CNN)谈到美国的警告时说:“我们不会给俄罗斯机会在这里制造惊喜，给乌克兰或世界带来一些东西。

“我们将确保尽可能透明、清晰地向世界展示我们所看到的东西，”他说。

俄罗斯已经部署了导弹、空军、海军和特种作战部队，以及补给来维持入侵。本周，俄罗斯将六艘两栖攻击舰开进黑海，增强了其在海岸登陆的能力。

普京否认有任何攻击乌克兰的意图。俄罗斯要求西方将前苏联国家排除在北约之外。它还希望北约不要在其边境附近部署武器，并从东欧撤回联盟部队——这些要求遭到西方的断然拒绝。

拜登和普京周六进行了一个多小时的谈话，但白宫没有暗示这一呼吁降低了欧洲即将爆发战争的威胁。

该公司表示，荷兰航空公司荷航取消了飞往乌克兰的航班，直到另行通知，这反映了西方的担忧。乌克兰包机航空公司天空之声周日表示，其从葡萄牙马德拉飞往基辅的航班被转移到摩尔多瓦首都。

乌克兰空中交通安全局发布声明，宣布黑海上空为“潜在危险区”，并建议飞机避免在2月14日至19日飞越该海域。

普京和拜登的对话是在普京和法国总统埃马纽埃尔·马克龙当天早些时候通话后进行的，当时正值俄罗斯和西方之间自冷战以来最大的安全危机的关键时刻。美国官员认为，他们只有几天的时间来阻止入侵和乌克兰的大规模流血事件。

德国总理奥拉夫·舒尔茨将于周一飞往基辅会见泽伦斯基，周二飞往莫斯科会见普京。

尽管美国和北约已经明确表示，他们不打算向乌克兰派兵打击俄罗斯，但美国和其他国家承诺的任何入侵和由此导致的惩罚性制裁，都可能产生远超前苏联共和国的反响，影响能源供应、全球市场和欧洲的力量平衡。

美国正在从基辅大使馆撤出大部分工作人员，并敦促所有美国公民立即离开乌克兰。英国和其他欧洲国家一起告诉其公民离开。

拜登加强了美国在欧洲的军事存在，作为对北约东翼盟友的保证。除了正在前往波兰的1700名士兵之外，还向波兰增派了3000名士兵。美国陆军也将1000名士兵从德国转移到罗马尼亚，罗马尼亚和波兰一样与乌克兰接壤。

自2014年以来，俄罗斯和乌克兰一直处于激烈的冲突之中，当时乌克兰亲克里姆林宫的领导人被民众起义赶下台。莫斯科的回应是吞并克里米亚半岛，然后支持乌克兰东部的分离主义叛乱，那里的战斗已造成1.4万多人死亡。

2015年由法国和德国斡旋达成的和平协议有助于停止大规模战斗，但常规的小规模冲突仍在继续，达成政治解决的努力也停滞不前。

US: Over 130,000 Russian troops now staged outside Ukraine

WASHINGTON -- Some airlines canceled flights to the Ukrainian capital and troops there unloaded fresh shipments of weapons from NATO members Sunday, as its president sought to project confidence in the face of U.S. warnings of possible invasion within days by a growing number of Russian forces.

President Volodymyr Zelenskyy spoke to President Joe Biden for about an hour, insisting that Ukrainians had the country under “safe and reliable protection” against feared attack by a far stronger Russian military, aides said afterward. The White House said both agreed to keep pushing both deterrence and diplomacy to try to stave off a feared Russian military offensive.

The Biden administration has become increasingly outspoken about its concerns that Russia will stage an incident in the coming days that would create a false pretext for an invasion of Ukraine.

U.S. and European intelligence findings in recent days have sparked worries that Russia may try to target a scheduled Ukrainian military exercise slated for Tuesday in eastern Ukraine to launch such a “false-flag operation,” according to two people familiar with the matter. They spoke on condition of anonymity because they were not authorized to speak publicly about it.

American intelligence officials believe targeting the military exercise is just one of multiple options that Russia has weighed as a possibility for a false-flag operation. The White House has underscored that they do not know with certainty if President Vladimir Putin has made a final determination to launch an invasion.

Moscow’s forces are massing on Ukraine’s north, east and south in what the Kremlin insists are military exercises.

A U.S. official updated the Biden administration's estimate for how many Russian forces are now staged near Ukraine's borders to more than 130,000, up from the more than 100,000 the U.S. has cited publicly in previous weeks. The official spoke on condition of anonymity to discuss the administration's conclusions.

Zelenskyy has repeatedly played down the U.S. warnings, questioning the increasingly strident statements from U.S. officials in recent days that Russia could be planning to invade as soon as midweek.

“We understand all the risks, we understand that there are risks,” he said in a broadcast Saturday. “If you, or anyone else, has additional information regarding a 100% Russian invasion starting on the 16th, please forward that information to us.”

But while Zelenskyy has urged against panic that he fears could undermine Ukraine's economy, he and his civilian and military leaders also are preparing defenses, soliciting and receiving a flow of arms from the U.S. and other NATO members.

A military cargo aircraft carrying U.S.-made Stinger anti-aircraft missiles and ammunition from NATO member Lithuania landed Sunday, bolstering the country’s defenses against any attack by air.

Zelenskyy wore military olive drab at a drill with tanks and helicopters near Ukraine's border with Russian-annexed Crimea this weekend. In the nearby city of Kalanchak, some expressed disbelief that Putin would really send his troops rolling into the country.

“I don’t believe Russia will attack us," said resident Boris Cherepenko. “I have friends in Sakhalin, in Krasnodar,” he said, naming Russian regions. "I don’t believe it.”

In Kyiv, others expressed uncertainty whether any Russian move would be economic, military, or happen at all. One woman, Alona Buznitskaya, speaking on a central street of the capital bearing a few signs declaring, “I love Ukraine,” said she was calm.

"You should always be ready for everything, and then you will have nothing to be afraid of,” she said.

The U.S. largely has not made public the evidence it says is underlying its most specific warnings on possible Russian planning or timing.

“We’re not going to give Russia the opportunity to conduct a surprise here, to spring something on Ukraine or the world,” Jake Sullivan, the U.S. national security adviser, told CNN on Sunday, about the U.S. warnings.

“We are going to make sure that we are laying out for the world what we see as transparently and plainly as we possibly can,” he said.

The Russians have deployed missile, air, naval and special operations forces, as well as supplies to sustain an invasion. This week, Russia moved six amphibious assault ships into the Black Sea, augmenting its capability to land on the coast.

Putin denies any intention of attacking Ukraine. Russia is demanding that the West keep former Soviet countries out of NATO. It also wants NATO to refrain from deploying weapons near its border and to roll back alliance forces from Eastern Europe — demands flatly rejected by the West.

Biden and Putin spoke for more than an hour Saturday, but the White House offered no suggestion that the call diminished the threat of an imminent war in Europe.

Reflecting the West's concerns, Dutch airline KLM has canceled flights to Ukraine until further notice, the company said. The Ukrainian charter airline SkyUp said Sunday its flight from Madeira, Portugal, to Kyiv was diverted to the Moldovan capital.

And Ukraine’s air traffic safety agency Ukraerorukh issued a statement declaring the airspace over the Black Sea to be a “zone of potential danger” and recommended that planes avoid flying over the sea Feb. 14-19.

The Putin-Biden conversation, following a call between Putin and French President Emmanuel Macron earlier in the day, came at a critical moment for what has become the biggest security crisis between Russia and the West since the Cold War. U.S. officials believe they have mere days to prevent an invasion and enormous bloodshed in Ukraine.

German Chancellor Olaf Scholz will fly to Kyiv on Monday to meet with Zelenskyy and Moscow on Tuesday to meet with Putin.

While the U.S. and NATO have made clear they do not intend to send troops to Ukraine to fight Russia, any invasion and resulting punishing sanctions promised by the U.S. and other countries could reverberate far beyond the former Soviet republic, affecting energy supplies, global markets and the power balance in Europe.

The United States was pulling most of its staff from the embassy in Kyiv and urged all American citizens to leave Ukraine immediately. Britain joined other European nations in telling its citizens to leave.

Biden has bolstered the U.S. military presence in Europe as reassurance to allies on NATO’s eastern flank. The 3,000 additional soldiers ordered to Poland come on top of 1,700 who are on their way there. The U.S. Army also is shifting 1,000 soldiers from Germany to Romania, which like Poland shares a border with Ukraine.

Russia and Ukraine have been locked in a bitter conflict since 2014, when Ukraine’s Kremlin-friendly leader was driven from office by a popular uprising. Moscow responded by annexing the Crimean Peninsula and then backing a separatist insurgency in eastern Ukraine, where fighting has killed over 14,000 people.

A 2015 peace deal brokered by France and Germany helped halt large-scale battles, but regular skirmishes have continued, and efforts to reach a political settlement have stalled.