WASHINGTON (AFP) - Syrian President Bashar al-Assad has denied in an interview with CBS television that he was behind a chemical attack last month and called on lawmakers to reject planned US military strikes, the US network said on Sunday.

"He denied that he had anything to do with the attack," CBS veteran correspondent Charlie Rose said, speaking after earlier interviewing Mr Assad in Syria.

"He denied that he knew there was a chemical attack, notwithstanding what has been said and notwithstanding the videotape. He said there's not enough evidence to make a conclusive judgment.

"The most important thing, as he says, is that 'there's no evidence that I used chemical weapons against my own people'," Mr Rose said.

Mr Assad's rare interview with an American network is to be aired on CBS on Monday.

The United States has led the charge that Mr Assad ordered a chemical attack against the residents of a Damascus suburb on Aug 21, which Washington says killed some 1,400 people including about 400 children.

Graphic videos released on Saturday showed dozens of people, including children, writhing on the ground with convulsions, some apparently foaming at the mouth and vomiting as rescuers sought to help them.

But Mr Assad challenged the US administration of President Barack Obama to provide the evidence as it seeks to build domestic and international support for military strikes against the Syrian regime for breaking international conventions with its alleged use of chemical weapons.

"He said that he did not necessarily know whether there was going to be a military strike. He said that they were obviously as prepared as they could be for a strike," Mr Rose added, citing his interview with Mr Assad.

The long-time Syrian leader also "had a message to the American people that it had not been a good experience for them to get involved in the Middle East in wars and conflicts," Mr Rose said.

"The results had not been good and they should not get involved and that they should communicate to their Congress and to their leadership in Washington not to authorise a strike."

Congress is due to begin full debate this week on whether to approve Mr Obama's plans for limited military strikes on Syria aimed at degrading its chemical weapons ability when it returns from its summer break on Monday.

But there is a deep scepticism among a war-weary American public over a new American military engagement in the Middle East.