DAMASCUS – Robert Ford, the first US ambassador to Syria since 2005, arrived Sunday in Damascus on a challenging mission to re-engage the two countries which disagree on a raft of important issues.

"United States Ambassador to Syria Robert Ford arrived in Damascus today in the afternoon," the embassy said in a statement.

"Ambassador Ford's appointment represents a tangible American action to try to find common interests between Syria and the United States through more regular and direct discussion with the Syrian government and people," it said.

An embassy source told AFP that Ford was due to submit his credentials to President Bashar al-Assad within the week and would not be having any official engagements before that.

Ford's arrival comes almost six years after Washington withdrew ambassador Margaret Scobey, days after the February 2005 assassination in Beirut of ex-premier Rafiq Hariri in a massive car bomb.

The attack was widely blamed on Syria but Damascus has always denied the allegations.

A career diplomat with wide knowledge of the Arab world, Ford's mission comes at a time of renewed tensions in neighbouring Lebanon, where the Syrian- and Iranian-backed Hezbollah and its allies quit the government on Wednesday over a UN-backed probe into Hariri's murder.

The appointment of Ford "shows that President (Barack) Obama wants to work with Syria even if we don't agree on every issue," a US embassy source said.

"The ambassador's first priority will be to deliver messages from the American government to the Syrian government," the source added, without elaborating.

The appointment should not be viewed as a "reward" for the Syrian government, State Department spokesman Philip Crowley said on January 7 as Ford was sworn in by Secretary of State Hillary Clinton.

In November Clinton told Lebanese An-Nahar newspaper that "Syria's behaviour has not met our hopes and expectations over the past 20 months."

Washington wants Syria to drop its support for the Islamist Hamas movement which controls the Gaza Strip as well as for Hezbollah, and to distance itself from its long-time ally Iran.

The United States has accused Syria and Iran of providing Hezbollah with missiles and sophisticated rockets which can threaten stability in Lebanon and the region.

Syria for its part wants the superpower to pressure Israel to pull out of the Golan Heights, which it has occupied since 1967, Syrian analyst Sami Moubayed told AFP.

Washington "is conscious of the necessity to engage a dialogue with Syria," said Moubayed, stressing however that Damascus would not "negotiate" its "solid" ties to Hezbollah.

Ford's arrival comes as the prosecutor of the Special Tribunal for Lebanon (STL), based in The Hague, is due Monday to submit the chargesheet which media reports have said will implicate Hezbollah members in the murder.

Prosecutor Daniel Bellemare will submit his findings to pre-trial judge Daniel Fransen at a hearing behind closed doors, and Hezbollah members will be targeted, French newspaper Le Monde said on its Internet site Saturday.

Last week Clinton accused Hezbollah and its allies of trying to wreck the UN probe, reiterating US support for the tribunal.

"We believe that the work of the special tribunal must go forward, so justice can be served and impunity ended," Clinton said in Qatar.

"We believe that the leaders of Lebanon have an ongoing responsibility to serve the interests of their own people, not outside forces," she said, apparently referring to Hezbollah allies Iran and Syria.

"Trying to bring the government down as a way to undermine the special tribunal is an abdication of responsibility but it also will not work."

Obama named Ford to the post last February, but because of Republican opposition was not able to confirm the appointment until December 29, when he bypassed Congress while it was not in session.

Ford is a veteran diplomat in the Arab world who has served as ambassador to Algeria and more recently as deputy chief of mission at the US embassy in Baghdad.

His wife, Alison Barkley, is a diplomat now serving in Saudi Arabia.