A top official at the State Department said Tuesday she was surprised when Poland announced a plan to supply Ukraine with fighter jets in its fight against Russia’s invasion. The plan, announced Tuesday, involved Poland sending all of its MIG-29 jets to a U.S. military base in Germany.

“I saw that announcement by the government of Poland as I was literally driving here today,” U.S. Undersecretary of State for Political Affairs Victoria Nuland said at a Senate Foreign Relations Committee hearing. “To my knowledge, it wasn’t pre-consulted with us that they planned to give these planes to us.”

Under the plan, the fighter jets would be handed over from the military to Ukrainian pilots. In return for providing their jets, Poland would receive U.S. jets “to help support backfill in their own security needs.” The Pentagon swiftly rejected the plan, describing it as “not tenable.”

“The prospect of fighter jets ‘at the disposal of the Government of the United States of America’ departing from a U.S./NATO base in Germany to fly into airspace that is contested with Russia over Ukraine raises serious concerns for the entire NATO alliance,” Pentagon Press Secretary John Kirby said in a statement. “It is simply not clear to us that there is a substantive rationale for it.”

Both Poland and Ukraine responded to the Pentagon’s rejection of the fighter jets plan Wednesday. Ukrainian President Volodymyr Zelenskyy reiterated his call for warplanes to Ukraine.

“This is not ping pong. This is about human lives,” Zelenskyy said. “We ask once again: solve it faster. Do not shift the responsibility, send us planes.”

Polish Prime Minister Mateusz Morawiecki said “Such a serious decision like handing over planes must be unanimous and unequivocally taken by all of the North Atlantic Alliance.”

Vice President Kamala Harris is expected to meet on Thursday with Prime Minister Morawiecki and Polish President Andrzej Sebastian Duda. The meeting is a part of a larger trip to Poland and Romania. A senior administration official who previewed the trip for the Associated Press on the condition of anonymity said Vice President Harris is expected to continue talks with the Poles about getting fighter jets to the Ukrainians.