Israeli Prime Minister Benjamin Netanyahu is set to escalate his campaign against US President Barack Obama's Iran diplomacy in a speech to Congress in Washington.
Tuesday's upcoming address has put unprecedented stress on the two leaders' relations, but Netanyahu said he meant no disrespect to Obama by accepting an invitation to speak by the president's rival Republicans.
As many as one-fifth of Democratic members plan to sit out the speech to protest against what they see as a politicisation of Israeli security, an issue on which Congress usually unites.
Netanyahu's aide said the prime minister would inform Congress of details on the closed-door talks designed to curb Iran's nuclear drive.
The White House is wary of the move, but Obama on Monday appeared to wave off any prospect the US alliance with Israel might be damaged long-term by the speech.
"I don't think it's permanently destructive," Obama told the Reuters news agency.
"I think that it is a distraction from what should be our focus. And our focus should be, 'How do we stop Iran from getting a nuclear weapon?'"
Netanyahu, who has played up his security credentials ahead of a closely contested March 17 election in Israel, has denied his speech would have any design other than national survival.
"I plan to speak about an Iranian regime that is threatening to destroy Israel," he told the pro-Israel US lobby - the American Israel Public Affairs Committee (AIPAC) - on Monday.
"The last thing that I would want is for Israel to become a partisan issue, and I regret that some people have misperceived my visit here this week as doing that."
Netanyahu wants the Iranians stripped of nuclear projects that might be used to develop a bomb - something Tehran insists it does not want. Washington deems the Israeli demand unrealistic.
Under a 2013 interim deal, the US and five other powers agreed in principle to let Iran maintain limited uranium enrichment technologies.
US national security adviser Susan Rice argued on Monday that this commitment could not be undone.
"As desirable as that would be it is neither realistic nor achievable," she told AIPAC.
"If that is our goal, our partners will abandon us and undermine the very sanctions we have imposed so effectively together," Rice added, urging US politicians not to intervene.