Russian President Vladimir Putin’s nuclear saber-rattling amounts to “empty threats,” Poland’s top diplomat argued during an appeal for Congress to authorize new aid to Ukraine.

“If he was to use these [nuclear] weapons, he would have to withdraw his troops from the front line, and the Ukrainians could take advantage of that,” Polish Foreign Minister Radoslaw Sikorski told the Atlantic Council during a visit to Washington, D.C. “And if he used the weapon, either on the battlefield or perhaps in the atmosphere, he would have to deal with a contaminated environment for which his army is not prepared. So actually, these, I think, mostly are empty threats that should not lead to us deterring ourselves from doing the right thing.”