US Secretary of State Mike Pompeo insisted Thursday that US troops will leave Syria, ahead of a keynote speech aiming to lay out a coherent US policy in the Middle East.

President Donald Trump's "decision to withdraw our troops has been made. We will do that. We will withdraw our forces, our uniformed forces, from Syria and continue America's crushing campaign," Pompeo told reporters.

Washington's top diplomat was speaking at a joint press conference with his Egyptian counterpart Sameh Shoukry on the third leg of a key Middle East tour.

He also met earlier with Egyptian President Abdel Fattah al-Sisi, after arriving in Cairo late Wednesday on his longest trip since taking office last year which has already taken him to Jordan, Baghdad and Arbil.

Later Thursday, Pompeo was to give a planned address entitled "A Force for Good: America Reinvigorated in the Middle East" at the American University in Cairo.

His tour is aimed at urging regional allies to continue to confront the "significant threats" posed by Iran and Islamic jihadists despite Trump's shock decision last month to pull all 2,000 American troops from Syria.

But the muddled pronouncements from the Trump administration, which swiftly walked back the planned withdrawal of troops from Syria, has triggered regional concern.

A senior State Department official insisted ahead of the trip the US will "not leave the Middle East."

The whistle-stop tour will also take Pompeo to Gulf countries including the United Arab Emirates, Bahrain, Qatar and Saudi Arabia.

As he arrived in Egypt, the State Department described the country as a "steadfast partner in the anti-terror fight, and a courageous voice in denouncing the radical Islamist ideology that fuels it".

But there are rising concerns that US policy is getting bogged down. A long-promised proposed Trump plan for a peace deal between Israelis and Palestinians has so far failed to materialise.

Ahead of his visit to Saudi Arabia in the coming days, Pompeo is also expected to confirm the strength of the US alliance with Saudi Arabia.

* This story was edited by Ahram Online.