The G7 group of nations has failed to reach agreement over threatening new sanctions against Russia and Syria.
The nations agreed there was no solution to the Syria crisis with President Assad in power.
Members of the G7 group of leading industrialised nations agreed to delay implementing sanctions until there was “hard and irrefutable evidence” over the alleged chemical attack, the BBC understands.
The diplomacy in the Italian town of Lucca follows the latest apparent use of chemical weapons in Syria.
He declared the talks “a political success”.
US Secretary of State Rex Tillerson will head to Moscow for talks on Syria, later on Tuesday.
What will US achieve in Moscow?
The fact that Rex Tillerson’s visit to Moscow is happening at all is telling, says BBC Moscow correspondent Steve Rosenberg.
Russia reacted angrily to last week’s US missile strike on Syria, condemning it as an “act of aggression”. Yet Moscow is happy to host the US secretary of state. He’ll meet his Russian counterpart Sergei Lavrov and a meeting with President Putin cannot be ruled out.
But experience shows that Moscow does not take well to threats or ultimatums. If America threatens Russia will additional sanctions, that is unlikely to force the Kremlin to change direction, our correspondent says.
If Mr Tillerson thinks he can weaken Moscow’s support for President Assad, he may need to re-think. The Syrian President is Russia’s key military ally in the Middle East. Russia has invested heavily – militarily, politically and financially – to keep him in power.