An Israeli cabinet minister has said relations with US President Donald Trump take priority over condemning neo-Nazis, to justify Prime Minister Benjamin Netanyahu's muted response to events in Charlottesville.

Critics have accused Netanyahu of being slow to condemn extremism and anti-Semitism at US far-right protests, having only done so in a single tweet - three days after the rally in the Virginia town that ended in bloodshed.

Ayoub Kara, the communications minister and a vocal Netanyahu supporter, said in remarks published Friday in the Jerusalem Post that backing Trump was a strategic must for Israel's right-wing government.

"Due to the terrific relations with the US, we need to put the declarations about the Nazis in the proper proportion," Kara told the English-language newspaper.

"We need to condemn anti-Semitism and any trace of Nazism, and I will do what I can as a minister to stop its spread. But Trump is the best US leader Israel has ever had."

"His relations with the prime minister of Israel are wonderful, and after enduring the terrible years of (Barack) Obama, Trump is the unquestioned leader of the free world, and we must not accept anyone harming him."

Netanyahu regularly speaks out against anti-Semitism in other countries, but the United States is Israel's most important ally, providing it with more than $3 billion per year in defence aid as well as key diplomatic backing.

Detractors have accused him of sacrificing his moral responsibility, especially to the US Jewish community, for strategic interests.

The protests last weekend saw neo-Nazis and white supremacists protesting outside a synagogue, chanting anti-Semitic slogans and giving the Nazi salute.

On Tuesday, Netanyahu released his only response so far to the rally.

"Outraged by expressions of anti-Semitism, neo-Nazism and racism. Everyone should oppose this hatred," the Jewish state's premier posted in English.

Trump has since reiterated earlier controversial claims that there was fault on "both sides," but Netanyahu has not commented further.

Trump's arrival in office in January was saluted by Netanyahu's government, considered the most rightwing in Israel's history, after a testy eight years with his predecessor Obama who often pressured the prime minster over Jewish settlement building in the occupied West Bank.