US President Joe Biden opened his first visit to the Mideast since taking office by reassuring Israeli leaders he would be willing to use force as a "last resort" to stop Iran's growing nuclear program.

The President's comments came in an interview with Israel's Channel 12 taped before he left Washington and broadcast on Wednesday, hours after the country's political leaders welcomed him with a red-carpet arrival ceremony at Tel Aviv's airport. 

"The only thing worse than the Iran that exists now is an Iran with nuclear weapons," Mr Biden said.

Asked about using military force against Iran, Mr Biden said: "If that was the last resort, yes." 

US ally Israel considers Iran to be its greatest enemy, citing its nuclear program, its calls for Israel's destruction and its support for hostile militant groups across the region.

The US and Israel are expected to unveil a joint declaration cementing their close military ties and strengthening past calls to take military action to halt Iran's nuclear program.

A senior Israeli official said before Mr Biden arrived that both countries would commit to "using all elements of their national power against the Iranian nuclear threat".

The official spoke on condition of anonymity pending the formal release of the statement.

Israeli leaders made clear as they marked Mr Biden's arrival that Iran's nuclear program was the top item on their agenda.

"We will discuss the need to renew a strong global coalition that will stop the Iranian nuclear program," said Israeli Prime Minister Yair Lapid, as he greeted the Democratic president at the airport ceremony in Tel Aviv.

Mr Biden said he would not remove Iran's Islamic Revolutionary Guard Corps from the US list of terrorist organisations, even if that kept Iran from rejoining the Iran nuclear deal.

Sanctions on the IRGC, which has carried out regional attacks, have been a sticking point in negotiations to bring Iran back into compliance with the agreement meant to keep it from having a nuclear weapon.

Iran announced last week that it had enriched uranium to 60 per cent purity, a technical step away from weapons-grade quality.

Iran insists its program is for peaceful purposes, though United Nations experts and Western intelligence agencies say Iran had an organised military nuclear program through 2003.

Biden greeted by caretaker prime minister

Mr Biden's visit to Israel follows the collapse of a coalition-led government headed by Naftali Bennett.

The President was greeted by Mr Lapid, the caretaker prime minister who is hoping to hang on to power when Israelis hold their fifth election in three years in November.

Mr Lapid reminded Mr Biden of when they first met roughly eight years earlier. Mr Biden was vice-president and Mr Lapid was finance minister. 

Mr Biden made reviving the Iran nuclear deal, brokered by Barack Obama in 2015 and abandoned by Donald Trump in 2018, a key priority as he entered office.

Mr Biden said Mr Trump made a "gigantic mistake" by withdrawing the US from the Iran nuclear deal.

"There are those who thought with the last administration we sort of walked away from the Middle East, that we were going to create a vacuum that China and/or Russia would fill, and we can't let that happen," he said.

But indirect talks for the US to re-enter the deal have stalled as Iran has made rapid gains in developing its nuclear program.

That has left the Biden administration increasingly pessimistic about resurrecting the deal, which placed significant restrictions on Iran's nuclear program in exchange for sanctions relief.

Biden visits Holocaust memorial

The President later visited the Yad Vashem memorial to Holocaust victims in Jerusalem.

Mr Biden, wearing a skullcap, was invited to rekindle the eternal flame in the memorial's Hall of Remembrance.

Two US marines placed a wreath on the stone crypt containing the ashes of Holocaust victims and Mr Biden listened as a cantor recited the remembrance prayer.

He then greeted two Holocaust survivors, kissing the women on their cheeks. His eyes welled with tears as he chatted with them.

"My mother would say 'God love you, dear,'" Mr Biden told the women.

One of the survivors, Rena Quint, 86, later said she told Mr Biden how her mother and brothers were killed in a death camp.

Ms Quint, who was born in Poland, said she was reunited with her father in a male slave labour factory, where she pretended to be a boy.

Her father was also murdered. She later was adopted by a childless Jewish couple after she arrived in the United States in 1946.

"He asked permission to kiss me and he kept on holding my hand and we were told not to touch him."

Mr Biden is set to meet Israeli officials on Thursday, including Mr Lapid, Israeli President Isaac Herzog and opposition leader and former prime minister Benjamin Netanyahu.

He will meet Palestinian officials on Friday. 

Mr Biden said he would emphasise in talks with Israeli and Palestinian leaders his continued support for a two-state solution to the Israeli-Palestinian conflict, but acknowledged that outcome likely would not be feasible "in the near term". 

He maintained that a two-state solution was the best way to ensure a "future of equal measure of freedom, prosperity and democracy for Israelis and Palestinians alike".

His national security adviser, Jake Sullivan, said Mr Biden would not offer any proposals during the trip aimed at restarting talks.

AP