Senator John Fetterman said he would consider leaving the Democratic party it ever became “the anti-Israel party”, as more than 100 House lawmakers backed halting military aid to the Middle Eastern ally over its incursions into Gaza and Lebanon.

The Pennsylvania senator has emerged as one of Israel’s most prominent advocates among Senate Democrats, even as others in the party back away from their traditional support for the country amid accusations that prime minister Benjamin Netanyahu’s government committed genocide in Gaza.

“My long term concern has been with the Democratic party, as I am a member of that, is that our party is going to back away and turn their back to Israel,” Fetterman said on Wednesday at an event organized by the Hill and NewsNation.

Nodding to recent primary victories by candidates who oppose aid to Israel, Fetterman said: “I’ve described that if our party ever becomes … the anti-Israel party, you know, that’s when I would leave.”

“That’s been a moral clarity for me,” he added.

While the senator acknowledged some attempts by Republicans to convince him to switch sides, he said he otherwise had no interest in doing so because he disagreed with the majority of the GOP’s policies.

“I’ve been very clear. I am never changing my party, except for that one condition that we just discussed,” Fetterman said. “If I was going to, I would have already done that.”

The senator spoke on the same day 103 House Democrats voted for an unsuccessful bid to halt $3.3bn in aid for Israel, the majority of which would be for its military. The Wednesday afternoon vote amounted to a significant rebuke of US policy towards the country, with some longstanding supporters of defense assistance for Israel saying that they could no longer justify sending it weapons.

“The American people are rightly demanding an end to a perpetual cycle of war, and the Netanyahu government cannot maintain its current course”, said the Democratic former House speaker Nancy Pelosi, adding that she voted yes “for the message that it sends”.

In April, a majority of Democratic senators voted for two attempts by independent Bernie Sanders to block the sale of bombs and bulldozers to Israel. Fetterman rejected both measures.