WASHINGTON — The Pentagon has rejected an offer from Poland to give its MiG-29 fighter jets to the US so they can be passed to Ukraine, saying it raises serious concerns for the NATO alliance.

The Pentagon said Tuesday that Poland’s offer raises serious concerns for the NATO alliance and the plan is not "a tenable one".

Pentagon Press Secretary John Kirby said in a statement that the prospect of jets departing from a US/NATO base in Germany to fly into airspace contested with Russia in the Ukraine war is concerning. He said it’s not clear to the US that there is a substantive rationale for it.

The US, he said, will continue to talk to Poland about the matter.

The plan — published in English on a Polish government website — would have seen Poland give its MiG-29 fleet to Ukraine in exchange for American F-16s. Washington would then have transferred them to Ukraine.

But in a statement published by the Pentagon, Washington rejected the idea.

"Poland's proposal shows just some of the complexities this issue presents. The prospect of fighter jets ‘at the disposal of the Government of the United States of America’ departing from a US/NATO base in Germany to fly into airspace that is contested with Russia over Ukraine raises serious concerns for the entire NATO alliance," the US statement said.

Ukrainian authorities say that Russian warplanes have carried new strikes on residential areas in eastern and central parts of the country.

An air alert was declared Wednesday morning in and around Kyiv, with residents urged to get to bomb shelters as quickly as possible.

“Kyiv region – air alert. Threat of a missile attack. Everyone immediately to shelters,” regional administration head Oleksiy Kuleba said on Telegram.

Thousands of people were evacuated from the eastern city of Sumy on Tuesday. But another attempt to move people to safety from the besieged southern port of Mariupol failed.

Ukrainian President Volodymyr Zelenskyy thanked the leaders of the United States and United Kingdom for banning Russian oil imports. He told the UK parliament that Ukraine would fight "on to the end".

Russian aircraft on Tuesday night bombed residential areas around Kharkiv, Ukraine’s second-largest city, and Zhytomyr, to the west of Kyiv, and its military also stepped up its shelling of Kyiv's suburbs, the Ukrainian emergency services said.

In Malyn, a town of 25,000 near Zhytomyr, the bombing killed at least five people, including two children, and destroyed a textile factory and seven homes, the agency said. Two people died, including a 7-year-old, in the bombing in Chuhuiv, near Kharkiv.

Ukrainian officials also reported dire conditions in the Kyiv suburbs of Bucha, Hostomel, Irpen, Vyshhorod and Borodianka, including bodies of the dead that couldn't be buried.

A humanitarian official said another 200 patients were stuck at Borodianka without food and medicines.

The mayor of Lviv said the city in far western Ukraine was struggling to feed and house the more than 200,000 people who have fled there. The displaced are being housed in the city's sport halls, schools and other buildings. — Agencies