WASHINGTON/JERUSALEM - Israeli Prime Minister Benjamin Netanyahu, who arrived in Washington on Sunday, is expected to speak in front of the US Congress with a hardline stance on Iran's nuclear program.

Netanyahu's controversial speech has further strained his sometimes prickly relationship with US President Barack Obama, putting the US-Israel ties to one of its toughest tests in years.

Netanyahu, who openly opposes the White House efforts to negotiate a nuclear deal with Iran, considers the Iranian nuclear project as an "existential threat" to Israel.

The prime minister hopes his speech on Tuesday will convince lawmakers and the American public that an initial framework agreement being negotiated between Iran and Western powers is "dangerous."

At the same time, US Secretary of State John Kerry and other international negotiators will be in Switzerland for talks with the Iranians, trying for a framework agreement before a late March deadline.

The P5+1 group, namely the United States, Britain, China, France, Russia and Germany, has been negotiating with Iran over its nuclear plan since mid-2013, and hoped to reach a final agreement by the end of March.

Whereas Washington and its allies are trying to get Iran to curb its nuclear program in exchange for lifting the international community's economic sanctions on Iran.

Netanyahu demands with a hardline stance that Iran give up its entire nuclear capabilities out of fear that Obama's Iran policy will allow its arch foe to develop an atom bomb. Iran, on its part, claims its nuclear program is aimed at peaceful purposes.

The prime minister is speaking in front of Congress at the request of Republicans. His visit was coordinated without the Obama administration's knowledge, deepening tensions between the two leaders whose relationship was frosty from the get-go.

Several leading members of America's political establishment have announced they plan to skip the address to a joint session of the US Congress.

And no meetings have been set up between Netanyahu and US government officials during his visit.

Critics have slammed the speech as an intervention into US politics and inappropriate given that Netanyahu is in the midst of a reelection campaign. Parliamentary polls are set for March 17.

Obama's National Security Adviser Susan Rice has been quoted as saying that the upcoming speech, which was coordinated behind the USgovernment's back, will play a "destructive" role in the close ties between the US and Israel.

However, Netanyahu insists that his speech is important amid the danger of nuclear Iran.

"I feel a representative of all Israeli citizens, also those who don't agree with me," Netanyahu said before boarding his plane.

"I feel a deep and honest concern about the security of all the citizens of Israel, the fate of the state and the fate of our people. I will do all in my power to safeguard our future," he said.

He reiterated that as prime minister of Israel, it's his obligation "to see to the security of Israel," therefore, "We strongly oppose the agreement being formulated with Iran and the major powers, which could endanger our very existence."

On the other hand, Israeli center-left politicians urged Netanyahu to cancel the trip, which they dubbed as political propaganda, which would hurt the US-Israel relations.

"What Netanyahu interested in is his political survival and not the state of Israel," former finance minister and head of the Yesh Atid party told Channel 2 on Saturday.

On Wednesday, US Secretary of State John Kerry slammed Netanyahu for his opposition to the ongoing talks, saying that the Israeli leader may have "a judgment that just may not be correct here."

But he also insisted the United States is eager to avoid politicizing the controversial visit.

"We don't want to see this turned into some great political football," said he.