Syrian Foreign Minister Walid al-Muallem on Tuesday said Syria has "already agreed" to an initiative by Russia for Damascus to hand over its chemical weapons stocks to international control.

"Yesterday, we had a round of very fruitful negotiations with (Russian Foreign Minister) Sergei Lavrov and he came forward with an initiative on chemical weapons," Muallem said in Moscow after meeting the speaker of the Russian lower house of parliament in comments quoted by Russian news agencies translated from Arabic.

Syria's main opposition group denounced on Tuesday as a "political maneuver" a Russian plan on Syria's chemical weapons, saying it is part of a useless procrastination.

"The proposal of Lavrov is a political maneuver and is part of useless procrastination that will only result in more deaths and destruction for the Syrian people," said an opposition statement.

Russia on Monday firmly stood by its ally Syria as President Bashar Assad's foreign minister visited Moscow, warning that military strikes against the regime would lead to an "outburst" of terrorism.

Russian Foreign Minister Sergei Lavrov, after talks with his Syrian counterpart Walid al-Muallem in Moscow, painted a dark picture of the consequences of U.S.-led military action and insisted the regime was still ready for talks.

Syria's foreign minister will on Monday travel to Moscow to discuss the crisis in his country with his Russian counterpart Sergei Lavrov, Moscow said.

Foreign Minister Walid Muallem's visit will come after a Saint Petersburg summit of 20 major developed and developing economies at which the Syrian crisis is expected to feature prominently.

U.S. Secretary of State John Kerry spoke Thursday with Syria's foreign minister about an alleged chemical weapons attack a day earlier that reportedly killed hundreds of civilians, an American official said.

Kerry discussed the attack on rebel-held areas near Damascus with Walid al-Muallem "to make clear that if, as they claimed, the Syrian regime has nothing to hide, it should have allowed immediate and unimpeded access to the site rather than continuing to attack the affected area to block access and destroy evidence," the official said.

A U.S. official has condemned the “campaign of intimidation and threats” carried out by the Syrian regime against Lebanon, saying it is a sign of Damascus' failure to abide by U.N. Security Council resolutions.

The official also slammed in remarks published in An Nahar daily on Sunday the letter sent by Syrian Foreign Minister Walid Muallem on June 13 to his Lebanese counterpart Adnan Mansour.

Syria will allow the Red Cross to enter Qusayr to aid trapped civilians only after the end of a regime assault on the embattled town, its foreign minister told the U.N. chief Sunday.

"Syrian authorities will allow the Red Cross in cooperation with the Syrian Red Crescent access to the area immediately after the end of military operations," Walid Muallem told Ban Ki-moon, state news agency SANA reported.

Russian Foreign Minister Sergei Lavrov on Tuesday slammed "extremists" within the Syrian opposition who he said were blocking the start of dialogue in the war-torn country by making unrealistic demands.

Speaking hours before meeting new U.S. Secretary of State John Kerry for the first time in Berlin, Lavrov said that recent faint hopes that dialogue was possible between the opposition and the regime of Bashar Assad had dissipated.

President Bashar Assad must fall, "all the killing" must end and the Syrian army must withdraw from all cities before any dialogue can begin with the regime, rebel chief Selim Idriss said on Monday.

The Free Syrian Army's chief of staff Idriss spoke to pan-Arab broadcaster Al-Arabiya after a groundbreaking statement in Moscow by Foreign Minister Walid al-Muallem that Assad's regime is "ready for dialogue with all who want dialogue, including those who are carrying arms".

The Syrian regime is ready to talk with all parties, including armed rebels, who want dialogue to end the conflict, Foreign Minister Walid al-Muallem said on Monday at talks with his Russian counterpart Sergei Lavrov.

"We are ready for dialogue with all who want dialogue, including those who are carrying arms," Muallem said at the Moscow talks with Lavrov, in an apparent reference to the rebels battling the regime of President Bashar Assad.