Nancy Pelosi
Nancy PelosiReuters

Rep. Nancy Pelosi (D-Calif.), the leader of the House Democrats, told reporters on Wednesday that she had warned Israeli Prime Minister Binyamin Netanyahu that his coming speech before Congress threatens to sink the nuclear talks between Iran and the United States.

"I think that such a presentation could send the wrong message," Pelosi told reporters during the Democrats' annual issues retreat in Philadelphia, according to The Hill. "That's my view, and I shared that with the prime minister today."

A Pelosi spokesman said Pelosi and Netanyahu spoke by phone earlier in the day. The spokesman declined to characterize Netanyahu's response.

House Speaker John Boehner (R-Ohio) raised eyebrows last week when he announced that Netanyahu had accepted his invitation to address a rare joint session of Congress early this year – an invitation extended without consulting Democratic leaders in Congress or the White House.

Boehner defended the action, saying Congress has every right, as a separate branch of government, to operate without the administration's input. Pelosi was quick to criticize Boehner's move and said it was a breach of protocol, adding such invitations to heads of state have always been preceded by consultations with leaders from the opposing party.

The White House originally gave an icy response to news that Netanyahu was invited to address Congress, saying it was a departure from diplomatic protocol. It later made clear that neither President Barack Obama nor Secretary of State John Kerry would meet Netanyahu while he is in Washington, explaining that American policy is not to meet foreign leaders on dates that are close to national elections in their countries.

Pelosi on Wednesday emphasized that Israel is a vital U.S. ally, and characterized Netanyahu as "a respected leader," but added she's also wary of the effect of the speech on the Iran talks.

"It's a serious big honor that we extend. That it should be extended two weeks before an election in a country without collaboration among the leaders of Congress, and without collaboration with the White House, is not appropriate," Pelosi said, according to The Hill.

"But the bigger issue is what would that do … to see how diplomacy will work or not [in the Iran talks]. If it doesn't work, we have to determine a course of action. But our strength in determining whatever course of action that is, I think, springs from the fact that we gave diplomacy a chance," she added.

Meanwhile, in what could be seen as a victory for Obama, a group of 10 Senate Democrats said on Tuesday they wouldn’t vote for new sanctions against Iran on the Senate floor until late March.

Obama has been vehemently opposed to new sanctions against Iran and has threatened to veto any legislation on the issue.