Poland is willing to hand its Mig-29 fighter jets to the United States, the foreign ministry said in a statement Tuesday, under a reported scheme that would see the planes given to Ukraine.

"Poland... is ready to deliver its Mig-29 planes to Ramstein airbase (in Germany) and make them available to the US for free and without delay," said Warsaw, which under a reported deal would receive F-16 fighters as replacements for the Soviet-era planes which Ukrainian pilots are trained on. 

US officials, including US Secretary of State Antony Blinken, had downplayed the possibility of any NATO country supplying besieged Ukraine. 

But speaking in Moldova Sunday, Blinken confirmed it was under active discussion. 

"Can't speak to a timeline, but I can just say we're looking at it very, very actively," he told reporters.

"We are looking actively now at the question of aeroplanes that Poland may provide to Ukraine and looking at how we might be able to backfill should Poland decide to supply those planes."

The comments came one day after Blinken met Ukraine's Foreign Minister Dmytro Kuleba on the Poland-Ukraine border and Kuleba pressed him for the aircraft.

Kuleba had said "the highest demand that we have is in fighter jets, attack aircraft, and air-defence systems."

"If we lose the skies, there will be much more blood on the ground," he said after the meeting, with Blinken standing beside him.

While a significant part of Ukraine's air force remains intact since the war began on February 24, both Ukraine and Russia have sustained significant losses and neither controls the airspace over the country.