Foreign Secretary Philip Hammond said Assad “can’t be part of Syria’s future.”

Britain has said Russia’s military build-up in Syria reinforces President Bashar al-Assad and increases Moscow’s “moral responsibility in the crimes committed by the regime.”

“Russia’s military build-up complicates the situation,” Foreign Secretary Philip Hammond told the French daily Le Monde in an interview after talks with his French and German counterparts in Paris on Thursday night.

“Assad must go, he can’t be part of Syria’s future,” Hammond added, according to Le Monde’s French translation. “If we reach a deal on a transition authority and Assad is part of it, then it will be necessary to talk with him in his capacity as an actor in this process.”

In remarks released on Thursday, Russia’s President Vladimir Putin said the only way to end the war in Syria is to support its existing government in the fight against terrorism.

In an interview with CBS News “60 Minutes,” the Russia leader repeated his view that only the Syrian people can decide if and when to replace Assad.

Russia has deployed a force equipped with attack jets, helicopters and armored vehicles to a Syrian airbase.

CBS interviewer Charlie Rose suggested that this Russian military intervention was designed to “rescue” Assad, and Putin replied: “Well, you’re right.”

“And it’s my deep belief that any actions to the contrary — in order to destroy the legitimate government — will create a situation which you can witness now in the other countries of the region or in other regions, for instance in Libya, where all the state institutions are disintegrated,” he said.

“We see a similar situation in Iraq,” he added.

“And there is no other solution to the Syrian crisis than strengthening the effective government structures and rendering them help in fighting terrorism, but at the same time urging them to engage in positive dialogue with the rational opposition and conduct reform.”

Next week Putin is to meet U.S. President Barack Obama on the sidelines of the U.N. General Assembly, but his latest comments only underline the gulf between the two leaders.