Israelis were wondering Sunday if hawkish Foreign Minister Avigdor Lieberman's defence of Washington's top diplomat was evidence of a change of heart or just a ploy to wrong-foot rightwing rivals.

Following weeks of cabinet ministers queuing up to attack US Secretary of State John Kerry and his efforts to nurture a peace deal, it was the outspoken Lieberman who on Friday stood up to defend him as "a true friend of Israel".

"Avigdor Lieberman continues to surprise," said the top-selling Yediot Aharonot daily of the tough-talking former bouncer who has frequently courted controversy with his outspoken statements, and who heads the far-right Yisrael Beitenu party.

"After stating from every podium that there was no chance of success for the negotiations with the Palestinians, the foreign minister has changed direction and embraced the Kerry initiative," the paper said.

In an unexpected twist, Lieberman rounded on coalition colleagues for their personal slurs against Kerry and his handling of Israel-Palestinian peace talks, singling out Economics Minister Naftali Bennett who heads the far-right national religious Jewish Home.

"We don't agree with Kerry over everything, but he is a true friend of Israel," he said in remarks broadcast on public radio.

"John Kerry is not a member of the settlers' council and he has a right to think differently than the screaming Naftali Bennett," he was quoted as saying by Haaretz newspaper.

Kerry, who is trying to hammer out a framework agreement to advance the talks, has faced a growing wave of attacks from government hardliners, most recently after warning last week that Israel would face growing delegitimisation if the negotiations collapsed in a speech which also referred to "talk of boycotts".

Cabinet ministers were quick to lash out, describing his comments as "offensive, unfair and intolerable", while others accused Kerry of not being an "honest broker" and one MP even suggested he had an anti-Semitic agenda, all of which prompted a series of sharp rebukes from Washington.

Little surprise, then, that Lieberman's public backing for Kerry was welcomed by a seemingly bemused State Department.

History of anti-Arab remarks

"It certainly is a powerful statement and a powerful message given his history and his background on these issues, and where his view was," spokeswoman Jen Psaki told reporters on Friday.

Known to his critics as the "Dobermann" of the right, Lieberman has a long history of making incendiary anti-Arab remarks. He derided Palestinian president Mahmud Abbas as a "diplomatic terrorist" and obstacle to peace, earning him a cold-shoulder from Washington.

He quit his cabinet post for more than a year to successfully fight corruption charges, returning to the foreign ministry in November with a markedly softer tone, urging colleagues to temper their public criticism of the US bid for a diplomatic resolution to the Iranian nuclear dispute.

The new-look Lieberman has won praise in the press as being the unexpected voice of reason in Prime Minister Benjamin Netanyahu's constantly squabbling rightwing coalition government.

"In his second term as foreign minister, Lieberman has tried to establish himself as the responsible adult in the coalition and as someone who holds moderate diplomatic positions," Yediot said.

"It's unclear whether this is a real change or just a political tactic aimed at providing him with a convenient jumping off point in the race for prime minister, but one thing is clear: the Americans really loved his speech."

In a separate commentary in the same paper, Sima Kadmon said that Lieberman's traditional power base of Russian-speaking immigrants had declined as they had been absorbed into mainstream society, forcing him to seek a new political strategy.

"Lieberman has made a decision. He is fed up being in the position he was in during his previous term in office, particularly when he saw no political gain from it either," she wrote.

No one should underestimate his political interest, she said of the firebrand hardliner whose burning ambition is to lead the Israeli right.

"The only way he is going to make his way to the Prime Minister's Bureau is by veering to the left, dividing the Likud and... rehabilitating his public image," she wrote.