"We welcome these agreements," Haidar was quoted as saying by the RIA Novosti agency. "On the one hand, they will help Syrians get out of the crisis, and on the other hand, they averted a war against Syria by removing the pretext for those who wanted to unleash one."
There has been no official statement from the Syrian government, and it was not clear whether Haidar's comments reflected Assad's thinking.
The deal, hashed out in marathon negotiations between U.S. and Russian diplomats, averts American missile strikes against the Assad regime, although the Obama administration has warned that the military option remains on the table if Damascus does not comply. President Barack Obama said last week the U.S. Navy will maintain its increased presence in the eastern Mediterranean Sea to keep pressure on Syria and to be in position to respond if diplomacy fails.
"The threat of force is real, and the Assad regime and all those taking part need to understand that President Obama and the United States are committed to achieve this goal," U.S. Secretary of State John Kerry said Sunday in Jerusalem, where he briefed Israeli leaders on the agreement.
He also said the agreement, if successful, "will have set a marker for the standard of behavior with respect to Iran and with respect North Korea and any rogue state, (or) group that tries to reach for these kind of weapons."
French President Francois Hollande said in a televised address to his country that he has not ruled out the "military option," either. Otherwise, he said, "there will be no pressure."
The U.S. accuses the Assad government of using poison gas against rebel-held suburbs of Damascus on Aug. 21, killing more than 1,400 people. Other death toll estimates are far lower. Syria denies the allegations and blames the rebels.
The suspected chemical attack raised the prospect of U.S.-led military action against Syria that the rebels hoped would tip the civil war in their favor. But as the strikes appeared imminent, the Parliament of key U.S. ally Britain voted against military action and Obama decided to ask Congress for authorization first, delaying an armed response.
Russia then floated the idea of Syria relinquishing its chemical arsenal to avert Western strikes, and the Assad regime quickly agreed. On Saturday, Moscow and Washington struck a framework agreement to secure and destroy Syria's chemical stockpile.
For Syria's opposition, the deal is disappointing in many ways. It defers any U.S. action for the foreseeable future and does nothing to address the broader civil war or the use of conventional weapons, which have been responsible for the vast majority of the more than 100,000 deaths in the conflict.
With that in mind, the main Western-backed Syrian opposition group called Sunday for a ban on the use of ballistic missiles and air power by Assad's forces in addition to the prohibition on chemical weapons.
"Chemical weapons attacks are a part of a bigger scheme of crimes against humanity committed by the Assad regime, including using the Syrian air forces and ballistic missiles on residential areas," the Syrian National Coalition said on its official website. "The Syrian Coalition insists that the prohibition of the use of chemical weapons, which killed more than 1,400 Syrian civilians, be extended to include the prohibition of the use of air forces and ballistic missiles on residential areas."
While a ban on air power and ballistic missiles would likely curb the bloodshed in some areas, it's unclear how such a measure would be imposed or enforced. The Syrian government is highly unlikely to unilaterally relinquish such weapons, while Western powers have shown little appetite for setting up a no-fly zone in the country, a costly and potentially dangerous endeavor.
Obama, speaking in a TV interview taped before Saturday's announcement of the chemical weapons deal, said Russian President Vladimir Putin is "protecting" Assad and doesn't share American "values" in Syria.
"He has a different attitude about the Assad regime," Obama told ABC's "This Week."
"But what I've also said to him directly is that we both have an interest in preventing chaos, we both have an interest in preventing terrorism. The situation in Syria right now is untenable. As long as Mr. Assad's in power, there is going be some sort of conflict there."
The U.S.-Russian agreement has won broad backing around the world, including from China, which is a permanent member of the U.N. Security Council. France also welcomed the deal, but French Foreign Minister Laurent Fabius cautioned during a visit Sunday in Beijing that it was only the "first stage."
In Cairo, the Arab League also supported the agreement.
"All parties are capable and influential enough to do their part in the U.N. Security Council to ensure a comprehensive cease-fire in Syria ... and to move toward negotiations in Geneva to achieve a peaceful settlement to the Syrian crisis," Secretary-General Nabil Elaraby said in a statement.
The deal was greeted with cautious optimism in Israel, where leaders expressed satisfaction that Syria, a bitter enemy, could be stripped of dangerous weapons but also pessimism about whether Assad will comply.
Standing next to Kerry in Jerusalem, Israeli Prime Minister Benjamin Netanyahu stressed his belief that the Geneva agreement would have deep repercussions for Iran, Syria's close ally.
"The world needs to ensure that radical regimes don't have weapons of mass destruction, because as we have learned in Syria, if rogue regimes have weapons of mass destruction, they will use them," Netanyahu said. "The determination the international community shows regarding Syria will have a direct impact on the Syrian regime's patron, Iran."
U.N. diplomats said U.N. Secretary-General Ban Ki-moon was expected to brief the Security Council on Monday about what its inspectors found from the sites of the suspected gas attack. They spoke anonymously because the timing was not yet final.
Germany offered Sunday to help destroy Syrian chemical weapons. Foreign Minister Guido Westerwelle said Berlin is "prepared to make a technical or financial contribution to the destruction of chemical weapons from Syria." He didn't elaborate, but officials say Germany has helped destroy chemical weapons in Libya and elsewhere in the past.
The Syrian opposition warned that the Assad regime may just be playing for time and said the threat of force must remain on the table. It added that securing Syria's chemical weapons "must be for achieving justice and bringing the perpetrators of chemical weapons to the international court."
The Syrian National Coalition also repeated its calls for military aid, to "force the regime to end its military campaign and accept a political solution that leads to the democratic transformation of Syria."
The U.S. and its allies have balked at sending heavy weapons to the rebels, fearful the arms could land in the hands of extremists who are among the most effective fighters in the opposition ranks. Washington announced plans months ago to deliver weapons to the opposition, but rebels say they have yet to receive anything.