Russia and the United States agree an objective investigation is needed into allegations that troops loyal to President Bashar Assad launched a chemical weapons attack in Syria, the Russian Foreign Ministry said on Friday.

It also said in a statement that Russia, Assad's key international ally in more than two years of civil war, had urged the Syrian government to allow a U.N. experts mission to investigate the allegations.

"The Russian side called on the Syrian government to cooperate with the UN chemical experts. It is now up to the opposition, which should guarantee safe access for the mission to the alleged place of the incident," the ministry said.
Moscow and Washington have often taken opposing positions on Syria but the ministry said Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry had agreed on the need for an independent investigation during a phone call on Thursday.

Russia, which has protected Assad from three consecutive UN Security Council resolutions aimed at pressuring him to end violence, said earlier this week that the alleged chemical attack, which killed hundreds of people, may have been a "provocation" by rebels meant to put the blame on Assad.

Syrian officials have called allegations against their forces "illogical and fabricated".

U.S. President Barack Obama said in an interview on Friday that the international community needs to find out more about whether chemical weapons have been used in Syria, and called on the Assad government to allow a full investigation.

"What we've seen indicates that this is clearly a big event, of grave concern," Obama said in a television interview with CNN. "The notion that the U.S. can somehow solve what is a sectarian complex problem inside of Syria sometimes is overstated"