乌克兰总统弗拉基米尔·泽伦斯基(Volodymyr Zelenskyy)一再热情呼吁美国和北约(NATO)通过恐吓或武力，在他的国家上空实施禁飞区，并禁止俄罗斯战机起飞。

但他也提出了另一个要求——乔·拜登总统的政府表示，正在与波兰等盟友合作，为战斗机补充乌克兰空军提供便利。

泽伦斯基在周一接受美国广播公司新闻频道(ABC News)的大卫·穆尔(David Muir)专访时表示:“我们知道这些苏联飞机驻扎在哪里，是哪些国家接待了它们，我们问过这些国家。”他补充说，拜登“可以做得更多，我相信他可以，我也愿意相信他有能力做到这一点。”

包括美国国务卿安东尼·布林肯在内的美国官员表示，政府正在努力解决这个问题，包括可能用美国喷气式飞机补充波兰空军。

但在美国国会议员越来越大的压力下，白宫和五角大楼周一表示，这不只是交出钥匙这么简单，尤其是在俄罗斯领导人弗拉基米尔·普京认为西方对乌克兰越来越多的军事援助正慢慢转向直接参与战争的情况下。

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美国国务卿安东尼·布林肯在新闻发布会上与波兰人交谈...

“我们当然不是在阻止、封锁或打击波兰——也就是说，他们是一个主权国家。他们自己做决定。但这不像调动飞机那么容易，”白宫新闻秘书珍·普萨基周一说。

“这只是在讨论这样一种可能性，如果有一个国家愿意向乌克兰人提供飞机，并要求美国予以回填——如果发生这种情况，那会是什么样子?”五角大楼发言人约翰·柯比随后表示。

普京警告说，任何试图在乌克兰上空实施“禁飞区”的国家都将“立即”成为“军事冲突的一方”——这种滑向更广泛战争的情况是美国和北约官员表示他们正在努力避免的。

但美国官员担心，增加美国的军事支持以包括战斗机可能会被视为普京走得太远。

美国和几个西方国家戏剧性地改变了他们愿意提供的援助，包括被称为“毒刺”的肩射防空导弹。长期反对向战区提供致命军事援助的德国，已经开始增加国防开支，并同意也提供毒刺。

据一名美国官员称，尽管奥巴马政府曾推迟提供被称为标枪的反坦克导弹，但拜登政府和其他美国盟友仅在过去几周内就提供了数千枚。

但到目前为止，这条线是针对军用飞机和先进的导弹防御系统的。

“除了帮助乌克兰人获得战斗机，让他们在北约的全面保护下飞离波兰机场，我们还需要为他们提供中远程防空系统，”前五角大楼高级官员、已退休的中情局官员米克·马尔罗伊(Mick Mulroy)说。“毒刺系统非常有效，但其射程有限。俄罗斯飞机飞行的高度让他们遥不可及。”

波兰官员对此表示强烈反对和深切担忧，担心普京会因为波兰支持乌克兰战斗机而袭击波兰机场。

普萨基对普京的角色置之不理，告诉记者，“我们不会等待弗拉基米尔·普京对我们在这里做什么的建议，因为这涉及到回填飞机。”但是她再次补充说，这是波兰的权利来决定。

目前，华沙似乎是反对的一方。波兰总理办公室周日在一条推文中称，有关该国将提供苏联时代米格-29战斗机和苏-25攻击机的报道是“假NEWS‼️”，并补充说，“波兰不会向#乌克兰派遣战斗机，也不会允许使用其机场。我们在许多其他领域也提供了大量帮助。”

据一些分析人士称，美国可能会提供足够的保护来安抚波兰的紧张情绪，并提供足够的支持来让波兰感到值得。

其中最主要的是向波兰提供更多的F-16战斗机。但这是一个漫长的过程，可能会使波兰在等待美国替代飞机时没有空中掩护。

无论如何，泽伦斯基和其他乌克兰官员表示，他们现在需要空中支持，包括泽伦斯基周六与300多名美国议员和工作人员举行的简报会，该简报会加强了两党对他的政府的支持。

自那以后的几天里，几位高级议员公开敦促拜登政府确保乌克兰获得更多战机，包括几位高级民主党人公开向总统施压。

参议院外交关系委员会主席、新泽西州民主党参议员鲍勃·梅嫩德斯在周一的一封信中敦促布林肯和国防部长劳埃德·奥斯丁敦促北约盟国“毫不拖延地”提供飞机

“要求他们提供自己的飞机，特别是在俄罗斯的军事侵略越来越接近他们自己的边界的时候，除非在最可怕的情况下，否则是不可想象的。不幸的是，这就是世界面临的情况。非常时期需要非常措施和牺牲，”他写给内阁官员。

与此同时，布林肯周一表示，美国最新一揽子军事援助中的大约70%已经在乌克兰手中，该援助总额为3.5亿美元，去年的援助额为10亿美元。

但他承认俄罗斯在军事上胜过乌克兰，称克里姆林宫“有能力继续压制乌克兰军队，当然也有能力对乌克兰人民采取可怕的行动，包括袭击平民。”

Ukraine pleads for Western warplanes. Will the US help deliver?

Ukraine President Volodymyr Zelenskyy has made repeated and passionate pleas now for the U.S. and NATO to implement a 'no-fly' zone over his country and ground Russian warplanes -- through intimidation or force.

But he's also made another ask -- one that President Joe Biden's administration said it is working with allies like Poland to facilitate -- for fighter jets to replenish the Ukrainian air force.

"We know where these Soviet planes are stationed, which countries host them, and we asked these countries," Zelenskyy told ABC News's David Muir in an exclusive interview Monday, adding Biden "can do more, I'm sure he can, and I would like to believe that, that he's capable of doing that."

U.S. officials, including Secretary of State Antony Blinken, have said the administration is working to address this, including by possibly replenishing Poland's air force with U.S. jets.

But amid growing pressure from U.S. lawmakers to do so, the White House and Pentagon said Monday it's not as simple as handing over keys -- especially as Russian leader Vladimir Putin eyes growing Western military aid for Ukraine as inching toward a direct role in the war.

"We are not, certainly, preventing or blocking or discouraging Poland -- that is, they are a sovereign country. They make their own decisions. But it is not as easy as moving planes around," White House press secretary Jen Psaki said Monday.

"It's just a discussion about the possibility of, should there be a nation that would want to give aircraft to the Ukrainians and would ask for a backfill from the United States -- should that happen, what would that look like?" Pentagon spokesperson John Kirby said shortly after.

Putin has warned that any country attempting to implement a 'no-fly' zone over Ukraine would "immediately" become "party to the military conflict" -- the kind of slide to a wider war that U.S. and NATO officials said they're working to avoid.

But U.S. officials are concerned that increasing U.S. military support to include warplanes could be seen as a step too far for Putin, too.

In dramatic fashion, the U.S. and several Western countries have shifted what aid they're willing to provide, including shoulder-fired anti-aircraft missiles known as Stingers. Germany, long opposed to providing lethal military aid to war zones, has moved to boost its defense spending and agreed to provide Stingers as well.

Whereas the Obama administration once held off on providing anti-tank missiles known as Javelins, the Biden administration and other U.S. allies have provided thousands in just the last couple weeks, according to a U.S. official.

But so far, that line has been drawn at military aircraft and advanced missile defense systems.

"In addition to assisting getting the Ukrainians fighter aircraft and letting them fly out of Polish airfields with full NATO protection, we need to provide them medium- and long-range air defense systems," said Mick Mulroy, a former top Pentagon official and retired CIA officer. "The Stinger system is very effective, but its range is limited. Russian planes are flying at altitudes that make them out of reach."

Polish officials have expressed strong opposition and deep concerns about precisely that, with the fear that Putin would strike Polish airfields for supporting Ukrainian fighter jets.

Psaki brushed aside Putin's role, telling reporters, "We're not waiting for the advice of Vladimir Putin on what we're going to do here as it relates to backfilling planes." But she added again it's Poland's right to decide.

For now, it seems Warsaw is the one opposed. The Polish prime minister's office called reports the country would provide Soviet-era MiG-29 fighter jets and Su-25 attack aircraft "FAKE NEWS‼️" in a tweet Sunday -- adding, "Poland won't send its fighter jets to #Ukraine as well as allow to use its airports. We significantly help in many other areas."

It's possible the U.S. could provide enough protection to calm Polish nerves and enough support to make it worth Poland's while, according to some analysts.

Chief among them would be giving Poland more F-16 fighter aircraft. But that's a lengthy process that could leave Poland without air cover as it waits on those U.S. replacement jets.

Either way, Zelenskyy and other Ukrainian officials said they need air support now, including during a briefing Zelenskyy held with more than 300 U.S. lawmakers and staff on Saturday that bolstered bipartisan support for his government.

In the days since, several top lawmakers have publicly urged the Biden administration to ensure Ukraine gets more warplanes, including several top Democrats openly pressuring the president.

Sen. Bob Menendez, D-N.J., the chair of the Senate Foreign Relations Committee, urged Blinken and Defense Secretary Lloyd Austin in a letter Monday to push NATO allies to provide aircraft "without delay."

"Asking them to provide their own aircraft, especially as Russia's military aggression edges closer to their own borders, would be unthinkable except in the direst circumstances. Unfortunately, that is the situation the world faces. Extraordinary times require extraordinary measures and sacrifices," he wrote to the cabinet officials.

In the meantime, some 70% of the latest package of U.S. military assistance -- which totaled $350 million and brought aid in the last year to $1 billion -- is already in Ukrainian hands, Blinken said Monday.

But he conceded Russia's military outguns and outmans Ukraine's, saying the Kremlin has "the ability to continue to grind down the Ukrainian military and, of course, to take horrific actions against the Ukrainian people, including attacking civilians."