DAMASCUS (Reuters) - Syrian Deputy Foreign Minister Faisal Mekdad on Thursday attacked US-backed Kurdish-led forces, saying they betrayed Syria and accused it of adopting a separatist agenda that gave Turkey a pretext to violate the country's sovereignty.

Asked whether Damascus would resume dialogue with Kurdish-led forces facing a Turkish offensive aimed at expelling them from northeastern Syria, Mekdad said: "These armed factions have betrayed their country and committed crimes against them."

"We will not accept any dialogue or conversation with those who have pledged themselves to outside powers. US agents will have no foothold on Syrian soil," he told a group of reporters in his Damascus office.

Al-Mekdad described the Turkish military intervention as "invasion and aggressive war waged by the Turkish regime on Syrian territory," noting that "the invasion of an independent sovereign country is an act outside the Charter of the United Nations and international law, and is in stark contrast to the UN Security Council resolutions on the crisis in Syria."

A Syrian Kurdish official said earlier this week that Kurdish-led authorities in northern Syria could hold talks with Damascus and Moscow to fill a security vacuum should US forces fully withdraw from the Turkish border region.

A senior military commander said one option for the Kurds would be to return the land to the Syrian government.

In the early days of the conflict, the Syrian government helped the powerful Kurdish YPG to take control of the mainly Kurdish cities, with Damascus shifting its focus to quelling popular protests against the rule of President Bashar al-Assad, which later turned into an armed insurgency.

The YPG did not fight the Syrian government during the war and absorbed the government presence in its main city (Qamishli) and has a lucrative illegal oil trade with Damascus.

But Damascus hates giving the Kurds autonomy as much as they seek. Assad's government earlier this year threatened Kurdish forces backed by Washington with a military defeat if it did not agree to return to state power.