Over Half of Americans Approve US Missile Strikes on Syrian Airfield

His comments ahead of a trip to Moscow followed condemnation from Russian Federation and Iran on USA airstrikes in Syria after a chemical weapons attack which killed more than 80 people, including up to 30 children.

Mr Putin and Iranian leader Hassan Rouhani warned the United States a "red line" had been crossed.

Members of the group also hope to gain a sense from U.S. Secretary of State Rex Tillerson of President Donald Trump's next steps and foreign-policy goals. A spokesman for Russian President Vladimir Putin called the strike an "aggression" and said the USA had violated worldwide law.

Putin said Russian Federation would be urgently asking the global chemical weapons watchdog - the Organisation for the Prohibition of Chemical Weapons - to investigate the incident.

Syrian army forces had been losing ground across the country until Russian Federation intervened militarily in September 2015, propping up Assad and protecting its own interests in the region. The U.S. and United Kingdom are already convinced of the Syria's government's guilt but other leaders want the investigation concluded before introducing any further measures.

"What we are focused on is building global support for a political solution to end the conflict and bring lasting peace and stability to Syria", he said.

President Vladimir Putin countered that Russian Federation had information that the United States was planning to launch new missile strikes on Syria, and that there were plans to fake chemicals weapons attacks.

But Johnson said Monday that "it is the Americans who have changed the game by using those cruise missiles", and it was right for the rest of the G-7 unite behind Tillerson.

"How is it possible that their forces were co-located with the Syrian forces that planned prepared and carried out this chemical weapons attack at the same installation and did not have foreknowledge?" said the official, speaking on condition of anonymity.

The official said that there might be a three-way meeting later this week in Moscow between officials from Russia, Syria and Iran.

A grass fire that broke out next to the Moscow airport where U.S. Secretary of State Rex Tillerson was due to arrive has been extinguished. "And we believe that the first priority is the defeat of ISIS", Tillerson said in an interview with CBS television's "Face the Nation" being broadcast later Sunday.

The next step would be to use United Nations talks to negotiate a political transition that could include Assad leaving power.

Although Russia has steadfastly supported Syrian President Bashar Assad's government, and they've coordinated military attacks together, Washington has never previously accused Moscow of complicity in any attack that involved the gassing of innocent civilians, including children. The U.S. has accused Russian Federation of having advanced knowledge of a pending chemical attack, while Moscow did nothing to stop it - and in fact, may have helped try to cover it up.