Israeli prime minister Benjamin Netanyahu, who arrived in the United States on Sunday, was expected to publicly air rift between his country and its closest ally, the US, over its possible nuclear deal with Iran.
In speeches on Monday and Tuesday, the Israeli leader is expected to make a case against the deal that many in his country fear will leave Iran with a substantial infrastructure to pursue the development of nuclear weapons when the accord expires.
If the negotiations succeed, faced with a March-end deadline, Iran's march towards nuclear weapons would be halted in return for the lifting of crippling economic sanctions.
Israel, and many American critics of Barack Obama administration's initiative, will settle for nothing short of a deal that completely dismantles Iran's nuclear infrastructure. Many in Obama's own party agree.
Netanyahu is expected to lay out his case in two separate speeches - the one on Monday is at the annual convention of AIPAC, America's most powerful pro-Israel lobby.
The second, the more widely watched and discussed of the two, will be on Capitol Hill, in a joint address, which has led to a rare public falling out of the two allies.
Netanyahu, who shares a testy relationship with Obama, is being seen in the US and in Israel as trying to exploit DC's partisan politics to score a point against the President.
The joint address invitation was extended to him by Speaker John Boehner, a Republican, who, some believe, should have cleared the visit with the administration. He didn't.
A miffed White House, which expected to be consulted on an international leader's visit, has said Obama won't meet Netanyahu, and nor would any of his senior officials.
Vice-president Joe Biden is abroad on a hurriedly organised tour, secretary of state John Kerry will be out of the country, too, in pursuit of the deal with Iran.
Officially, the White House doesn't want to receive Netanyahu, saying the Israeli leader faces an election in a few days at home and the US can't be seen as taking sides.
But the administration is clearly annoyed, and has done little to conceal it. In a TV interview, national security adviser Susan Rice called Netanyahu's decision to speak "destructive".
Kerry tried to dial down the temperature on Sunday saying Netanyahu is welcome to speak in the US, but even he couldn't help a swipe calling the visit "odd, but not unique".