US top diplomat Mike Pompeo planned to visit Jerusalem's Western Wall alongside Israeli Prime Minister Benjamin Netanyahu on Thursday in what would be a break with longstanding diplomatic practice.

Two former US diplomats could not recall such a high-ranking US official visiting the site with an Israeli premier, which could be taken as tacit approval of Israel's sovereignty over the location in annexed east Jerusalem.

The visit comes less than three weeks before Israeli elections in which Netanyahu is facing a tough challenge from a centrist alliance led by a former military chief of staff.

“The trip to the wall is something that I've been talking with PM Netanyahu about doing some time ago. It's our first chance to go there together,” Pompeo told journalists before the visit on Thursday.

“I think it's important. I think it's symbolic that a senior American official go there with a PM of Israel,” he added, calling it “a place that's important to many faiths.”

Donald Trump became the first sitting American president to visit the wall, the holiest site where Jews are allowed to pray, during his trip in May 2017.

US Vice President Mike Pence also visited the Western Wall during his visit in January 2018.

Neither were accompanied by Israeli leaders during the hugely symbolic visits.

Pompeo said he did not know why neither Trump nor Pence visited the site with Netanyahu, and declined to say whether it indicated a change in how the United States sees the status of the Western Wall.

“I'm looking forward to going to the wall with the PM,” he said.

Israel occupied east Jerusalem in the 1967 Six-Day War and later annexed it in a move never recognised by the international community.

It considers the entire city its capital, while the Palestinians see the eastern sector as the capital of their future state.

In 2017, Trump controversially recognised Jerusalem as Israel's capital and announced the move of the US embassy there, breaking with decades of international consensus.