Lawyers for the Uzbek man charged in the 2017 truck attack that killed eight people on a Manhattan bike path asked a judge Thursday to bar the government from seeking the death penalty, saying the decision, which ultimately rests with Attorney General Jeff Sessions, had become too politicized.

The lawyers cited Mr. Trump’s emphatic tweets calling for the execution of their client, Sayfullo Saipov, and another more recent tweet that suggested political considerations should inform the Justice Department’s charging decisions. They also pointed to reports that Mr. Trump had considered firing Mr. Sessions for not following his wishes.

“Mr. Sessions works for President Trump and obviously wants to keep his job,” Mr. Saipov’s federal public defenders wrote. “It defies reality, not to mention all appearances, to believe that he could make a truly independent decision as to whether Mr. Saipov should face the death penalty, knowing that a decision not to seek death would inevitably trigger a ‘tweetstorm’ of ridicule and scorn from the President and might well lead to the loss of his job.”

The lawyers argued, as an alternative, that the judge, Vernon S. Broderick of Federal District Court in Manhattan, should appoint an independent prosecutor to decide if the death penalty was warranted, a decision Mr. Sessions has yet to announce.