BEIRUT (Reuters) - Islamic State suicide bombers on Sunday attacked a military base for U.S.-backed fighters near the Syrian-Iraqi border, leaving several dead before blowing themselves up, rebel sources and the militants said on Sunday.

They said the dawn attack on the heavily defended military camp near the Syrian al Tanf border crossing with Iraq involved at least one explosive-laden vehicle that rammed the gate of the base which was set up by the fledgling, Pentagon-trained New Syria Army.

Another rebel said the militants were not able to storm the heavily fortified camp where large sand barriers have been erected to prevent such incursions and attacks in an area where the militants operate with hit and run attacks.

"It's a well defended camp and they tried to storm it but the suicide vehicle was targeted and hit," said Said Seif al Qalamoni, a rebel familiar with operating in the same area. He added that there were at least one dead and several wounded.

Qalamoni said jets from the U.S.-led coalition against Islamic State shortly after struck at several vehicles believed to be driven by the militants in the sparsely populated desert area.

Amaq, a news agency affiliated to Islamic State, said two suicide bombers had attacked the camp and detonated an explosive-laden car before storming the compound and detonating their suicide vests.

The New Syria Army was formed around 18 months ago using insurgents driven from eastern Syria at the height of Islamic State's rapid expansion in 2014.

Diplomats and rebel sources say U.S. special forces are training hundreds of fighters from the group in camps in Jordan.

The Tanf crossing, which was captured from Islamic State militants last year, is a 240 km (150 miles) drive from Syria's ancient city of Palmyra, also known as Tadmur.

Scores of Islamic State militants moved south into southern Syria and the Tanf area after they were driven out of Palmyra in central Syria this year.

The militants, who control a swathe of territory spreading from Iraq into central Syria, still control the al-Bukamal Syria-Iraq border crossing near Deir al Zour.

The New Syria Army, with the backing of Western special forces and U.S.-led air strikes, launched an attack last June from the Tanf base on al-Bukamal northeast of Tanf.

But the operation, which aimed to capture the town and cut supply lines for the group between Syria and Iraq, failed after rebels were encircled on the approaches of the town after the jihadists mounted a counter-attack.[L8N19L0D3]

The New Syria Army's base in Tanf has been hit twice previously by Russian air strikes, even after the U.S. military used emergency channels to ask Moscow to stop after the first strike, U.S. officials say.

(Reporting by Suleiman Al-Khalidi; Editing by Stephen Powell)