Secretary of State John Kerry openly questioned Mr Netanyahu’s judgment on the issue on Wednesday.
The comments injected new tension into an already strained relationship between the close allies ahead of Mr Netanyahu’s address to Congress next Tuesday.
More Democratic politicians announced they would skip the speech, which was orchestrated by Republican leaders without the knowledge of President Barack Obama’s White House.
Mr Netanyahu hopes his speech will strengthen opposition to a potential nuclear deal with Iran, Mr Obama’s signature foreign policy objective.
US and Iranian officials reported progress in negotiations this week on a deal that would clamp down on Tehran’s nuclear activities for at least ten years but then slowly ease restrictions. Mr Netanyahu lashed out at the US and other usual staunch allies of Israel.
“It appears that they have given up on that commitment and are accepting that Iran will gradually, within a few years, will develop capabilities to produce material for many nuclear weapons,” he said in Israel.
“They might accept this but I am not willing to accept this,” he said in remarks delivered in Hebrew and translated.
“I respect the White House, I respect the President of the United States, but in such a fateful matter that can determine if we exist or not, it is my duty to do everything to prevent this great danger to the state of Israel,” he said.
Mr Kerry, testifying at a congressional hearing, dismissed Mr Netanyahu’s worries. He argued that a 2013 interim agreement with Iran that the Israeli prime minister also opposed had in fact made Israel safer by freezing key aspects of the Islamic republic’s nuclear programme.
“He may have a judgment that just may not be correct here,” Mr Kerry said.
His comments, as well as statements from other top US officials, made clear the Obama administration had no plans to mask its frustrations during Mr Netanyahu’s visit.
National security adviser Susan Rice said plans for Mr Netanyahu’s speech had “injected a degree of partisanship” into a US-Israel relationship that should be above politics.
“It’s destructive to the fabric of the relationship,” Ms Rice told a US chat show. “It’s always been bipartisan. We need to keep it that way.”
Mr Netanyahu’s plans have put Democrats in a difficult spot – fearing they will look anti-Israel if they don’t attend.