Poland's prime minister on Wednesday said his country was prepared to make planes available to Ukraine, but that it would only do so through the NATO alliance.
Warsaw had come up with a plan to transfer its Russian-made fighter planes to a US military base to be passed on to Ukraine as the Russian invasion draws close to its third week, but this was dismissed by Washington.
What did Warsaw say?
Polish Prime Minister Mateusz Morawiecki said a decision about providing his country's fighter jets to Ukraine needed to be a joint decision made by NATO members.
"We did not agree to supply planes by ourselves because it must be the decision of the whole of NATO," he said during a press conference on Polish television.
"The USA does not want these planes to come to Ukraine from American bases," the adviser, Jakub Kumoch, told public broadcaster TVP Info. "Poland is ready to act, but only within the framework of the alliance, within the framework of NATO."
Poland's decision to put the plan on ice comes before US Vice President Kamala Harris arrives for a visit to focus on the next steps in response to Russia's invasion of Ukraine.
What was the Polish proposal?
Poland had outlined a plan to take its 28 MiG-29 fighters, which would be familiar to Ukrainian pilots, to the US Ramstein airbase in Germany.
The expectation was that the aircraft would eventually be handed over to the Ukrainian air force.
The United States would, in return, then have supplied Poland with US-made jets that had the "corresponding capabilities," such as the F-16s that are already a mainstay of the Polish air force.
However, the Poles hadn't first cleared that idea with the Biden administration, and the idea was quickly dismissed by the Pentagon.
Why is the West wary?
While the gift of MiG-29s would be a morale booster for Ukrainians, it would also risk the possibility of the war spreading beyond the country.
Russia has already warned other nations and parties not to get involved in the conflict. The Kremlin said on Wednesday that Poland's offer of fighter jets was "highly undesirable and a potentially dangerous scenario."
Questions also remain over whether the planes would be enough to influence the course of fighting in Ukraine. The number of aircraft is relatively small and the MiG-29s also are inferior to more sophisticated Russian planes. They could possibly easily be targeted by Russian pilots and Russian missiles.
What is the Ukrainian position?
Ukrainian President Volodymyr Zelenskyy on Tuesday denounced what he called the West's unkept "promises" to protect Ukraine from Russian attacks. He said assurances received so far have not been fulfilled.
Zelenskyy said on Wednesday the international community would be responsible for a mass "humanitarian catastrophe" if it did not agree a no-fly zone to protect his country.
"When will there be a decision? Look, we're at war!" Zelenskyy said in a video on his Telegram channel. "We ask you again to decide as soon as possible. Send us planes."
Establishing a no-fly zone over Ukraine, something also sought by Zelenskyy, has been rejected by Washington and NATO.
Russian President Vladimir Putin has threatened "colossal and catastrophic consequences" for Europe and the wider world, should a no-fly zone be implemented.
US vice president pays a visit
US Vice President Kamala Harris is traveling to Poland on Wednesday for what was planned to be a chance to thank Warsaw for taking in hundreds of thousands of Ukrainians fleeing their country after Russia's invasion.
She's also visiting Romania and is widely expected to reassure both countries of Washington's support.
Both Bucharest and Warsaw are increasingly wary of Russia's increased aggression in the region and are NATO's easternmost members. They each share a border with Ukraine, where thousands of refugees are arriving each day.
Harris is also expected to look at how NATO members can implement the economic sanctions put in place and remain aligned and move forward together.
She is due to talk to Ukrainian refugees in Poland and will discuss the war-related issues with Canada's Prime Minister Justin Trudeau, who is also visiting Warsaw after meeting German Chancellor Olaf Scholz in Berlin on Wednesday.