Syrian President Bashar al-Assad (pic) should seize an opening for dialogue to end the conflict, a US official said Monday, voicing Washington's strong backing for the move by Syria's opposition chief.

Ahmed Moaz al-Khatib, the leader of the Syrian Opposition Coalition, last week announced he was ready for talks with the Damascus regime -- subject to conditions, including the release of 160,000 detainees.

He reiterated the call on Monday, urging Assad to respond positively and to delegate his deputy, Vice President Faruq al-Sharaa, help negotiate an end to the 22-month war that has cost tens of thousands of lives.

"If the regime has any interest in peace, it should sit down and talk now with the Syrian Opposition Coalition, and we would strongly support al-Khatib in that call," State Department spokeswoman Victoria Nuland said.

But she stressed to journalists that the US position remained unchanged on bringing to account those, on both sides, who have committed atrocities.

"We've long said that those with blood on their hands in Syria need to be held accountable, that it's up to the Syrian people to determine how they should be held accountable."

Assad last month announced he was ready for talks with the opposition, but ruled out meeting groups, such as Khatib's coalition, which back armed rebels seeking to overthrow his regime.

Some opposition figures have denounced Khatib's proposal as a betrayal of their struggle.

But Khatib rejected the criticism, telling the pan-Arab channel Al-Jazeera: "Our people are dying, and we will not allow that."