The two men have known each other since the 1980s

US President Donald Trump was scheduled to host Israeli Prime Minister Benjamin Netanyahu at the White House on Wednesday, their first meeting since the inauguration and one that promises to shape the contours of Middle East policy for the years ahead.

On the agenda are some of the region's most volatile issues: the war in Syria, the Iran nuclear file and the Israeli-Palestinian conflict, including Israel's settlement-building on occupied land and whether a Palestinian state will emerge.

Netanyahu, under investigation at home over allegations of abuse of office, spent much of Tuesday huddled with senior advisers in Washington preparing for the talks. Officials said they wanted no gaps to emerge between US and Israeli thinking during the scheduled two-hour Oval Office meeting.

Attention will also be paid to body language. While the two men have known each other since the 1980s, Trump has shown a tendency when meeting other leaders to throw them off balance with lengthy, domineering handshakes.

For Netanyahu, a conservative who has spent 11 years in power but never previously overlapped with a Republican president, the gathering is an opportunity to reset ties after a frequently combative relationship with Barack Obama.

Dennis Ross, an Iran specialist, said both parties had a vested interest in a successful meeting.

"It's going to succeed in no small part because both President Trump and Prime Minister Netanyahu have a very big stake in wanting to demonstrate that whatever the problems were with the last administration, they are now gone," Ross said. "And that in no small part they were attributable to the last administration, meaning to president Obama."

Common ground?

Social media exchanges suggested a budding bromance between Netanyahu and Trump, who has pledged to be the "best friend" Israel has ever had in the White House. But the US president has more recently tempered his pro-Israel stance.

Trump, who has been in office less than four weeks and has already been immersed in problems including the forced resignation of his national security adviser, brings with him an unpredictability that Netanyahu's staff hope will not impinge on the discussions.

During the election campaign, Trump was pro-Israel in his rhetoric, promising to move the US embassy from Tel Aviv to Jerusalem, backing David Friedman, a supporter of settlements, as his Israeli envoy and saying that he would not put pressure on Israel to negotiate with the Palestinians.

That tune, which was music to Netanyahu's ears and to the increasingly restive right-wing within his coalition, has since changed, making Wednesday's talks critical for clarity.