"Congratulations @JoeBiden and @KamalaHarris. Joe, we've had a long & warm personal relationship for nearly 40 years, and I know you as a great friend of Israel. I look forward to working with both of you to further strengthen the special alliance between the US and Israel," Netanyahu said on his Twitter account, which still carries a photograph of him and incumbent US President Donald Trump at its head.

Having been in lockstep with Trump for four years, Netanyahu will be challenged by any departure by Biden from Trump's tough policy on Iran and toward the Palestinians. Biden has pledged to restore US involvement in the 2015 Iran nuclear deal - which Trump had pulled out of - and may oppose Israeli settlement of occupied land where Palestinians seek statehood.

Netanyahu thanked Trump in a subsequent tweet:

"Thank you @realDonaldTrump for the friendship you have shown the state of Israel and me personally, for recognising Jerusalem and the Golan, for standing up to Iran, for the historic peace accords and for bringing the American-Israeli alliance to unprecedented heights."

Netanyahu's message came hours after many world leaders had already congratulated Democrat Biden, even as Trump refused to concede and pressed ahead with legal fights against the outcome.

A spokesman for Netanyahu did not respond to a request for comment on the relative delay. Dani Dayan, Israel's former consul to New York said Netanyahu's slowed response was a precautionary move.

"There is a president in the White House who has not yet acknowledged his defeat and whose whims definitely play a major role in his decision making process and he will be sitting in the White House for another two and a half months," Dayan told Army Radio.

The right-wing Netanyahu's particularly close ties with Trump followed an acrimonious relationship with his predecessor Barack Obama, which some critics said compromised US bipartisan support for Israel.

Among Israelis, Trump has won overwhelming popularity and many may be sad to see him go.

Meanwhile, Palestinian President Mahmoud Abbas congratulated the US President-elect and indicated the Palestinian leadership would drop its three-year political boycott of the White House.

"I look forward to working with the President-elect and his administration to strengthen the Palestinian-American relations and to achieve freedom, independence, justice and dignity for our people, as well as to work for peace, stability and security for all in our region and the world." Abbas said in a statement issued from his office in the West Bank city of Ramallah.

Abbas ended all political dealings with Donald Trump's administration after its 2017 decision to recognise Jerusalem as Israel's capital and move the US Embassy there.

Australian Associated Press