US pressing Gulf states to keep Syria isolated - sources

* Washington wants Gulf states to maintain distance from Assad

* Lobbying comes come after UAE moves closer to Damascus

* Syrian leader needs outside help to rebuild country after war

* Some see risk of Iran filling void if Assad is isolated

By Ghaida Ghantous and Michael Georgy

DUBAI, Feb 18 (Reuters) - The United States is lobbying Gulf states to hold off restoring ties with Syria, including the UAE which has moved closer to Damascus to counter the influence of its rival Iran, five sources told Reuters.

The opposing approaches are an early test of whether Syrian President Bashar al-Assad can gain political and diplomatic credibility after a nearly eight-year civil war turned him into an international pariah.

Many countries cut links with Syria at the start of the war.

Several Gulf states shut or downgraded their embassies, Syria was suspended from the Arab League, flights stopped and border crossings were closed. The United States and other countries imposed economic sanctions.

Washington, backed by Gulf countries Saudi Arabia and Qatar, does not want Syria welcomed back into the international community until a political process to end the war is agreed.

"The Saudis are quite helpful in pressing the others. Qatar also is doing the right thing," said a U.S. official, when asked about the diplomatic pressure.

The official said that the United States was pleased that "some Gulf states are putting the brakes on".

The U.S. position suggests that Assad is still a long way from being accepted, even after his forces reclaimed most of Syria through victories over Sunni rebels, thanks largely to help from Iran and Russia.

The lack of support from Washington and regional heavyweight Riyadh to end Syria's isolation will make it harder for the devastated country to attract investment needed to rebuild it.

While the UAE believes Sunni Muslim states must embrace Syria swiftly in order to move Assad out of Shi'ite Iran's orbit, Saudi Arabia and Qatar back the U.S. approach.

The UAE sees Assad as the "only option", according to one Gulf source, and believes that stemming Iranian influence in Syria could help prevent the kind of hold it now has in Iraq.

During the war, the UAE did support armed groups opposed to Assad. But its role was less prominent than that of Saudi Arabia and Qatar, and its support was mostly to do with ensuring that Islamist forces did not dominate the uprising.

U.S. and Saudi officials have spoken to representatives of other Gulf countries, urging them not to restore ties with Syria, three Gulf political sources, a U.S. official and a senior Western diplomat said.