US' promise to outstay Iran in Syria not necessarily through a 'military presence', says official

The US promise to outstay rival Iran in Syria has been reworded, with a senior official saying on Thursday that Washington's presence in the war-torn country will not necessarily be a military one.

James Jeffrey, the US special representative on Syria, claimed that comments by officials that Washington will stay indefinitely in Syria to counter Iran does not necessarily mean that soldiers will remain in the country.

He said such actions would counter the mission officially set by former President Barack Obama who said the goal of Washington in Syria was to defeat the Islamic State group.

Current President Donald Trump has repeatedly said he wants to withdraw US troops from the country, despite security experts saying this would benefit IS.

Recently it was suggested that the US would only pull out of Syria, if Iran did so first.

"The president wants us in Syria until that and the other conditions are met," Jeffrey told reporters on the sidelines of the United Nations meeting. 

He then added: "'Us' is not necessarily American boots on the ground.

"There are many ways that we can be on the ground. We're certainly on the ground diplomatically," he said.

Jeffrey added that no options were definite.

"Boots on the ground have the current mission of the enduring defeat of [IS]," he said.

There are around 2,000 US troops in Syria, most of them advising the Syrian Democratic Forces, an anti-IS militia of mostly Kurdish fighters who have occasionally clashes with pro-regime Iranian militias.

Trump's national security adviser John Bolton is more hawkish towards Iran, and believes the US should counter Tehran's influence in the region.

This includes Syria, where thousands of Iranian troops and militia fighters are backing pro-regime forces.

"We're not going to leave as long as Iranian troops are outside Iranian borders."

Iran also backs Lebanese Shia movement Hizballah, which has thousands of fighters in Syria, backing Assad's forces.

After initially downplaying its military presence in Syria, Tehran now claims its troops are there at the request of the Syrian government.

Iran President Hassan Rouhani has also rejected the Trump administration's warnings regarding Syria.

Relations between Iran and the US have hit a new low, with Washington withdrawing earlier this year from a nuclear deal with Tehran.

Iran has been accused of being behind unrest in Yemen, Iraq, Bahrain, Saudi Arabia and Lebanon.