BERLIN (Reuters) – German Chancellor Angela Merkel expects the Kremlin to use its influence with the Syrian government to prevent a humanitarian disaster in the rebel-held northern region of Idlib, a government spokeswoman said on Friday.

Merkel has raised the issue in recent days with both U.S. President Donald Trump and Russian President Vladimir Putin, and the German government is watching developments in the region with growing concern.

“We expect … Russia to prevent the Syrian government from escalating the situation and thereby prevent a humanitarian catastrophe,” Merkel’s spokeswoman Ulrike Demmer told a regular government news conference.

She said it was imperative that humanitarian organizations be given unfettered access to the affected civilian population.

Syrian Foreign Minister Walid al-Moualem said on Thursday government forces will “go all the way” in a planned offensive in Idlib, the last major insurgent bastion in Syria, and that Damascus’s main targets were Islamist al-Nusra militants.

But he said Syria would not use chemical weapons in any offensive and that it did not have such arsenal. Syria would try to avoid civilian deaths, Moualem added.

Russia, meanwhile, has said it will begin a major naval exercise in the Mediterranean on Saturday, a move that appeared to be aimed at deterring Western forces from carrying out strikes on Syrian government forces.

The United Nations has called on Russia, Iran and Turkey to delay a battle that could affect millions of civilians, calling for humanitarian corridors to evacuate civilians.

Putin will attend a three-way summit in Tehran on Sept. 7 with the leaders of Turkey and Iran, his spokesman said.

(Reporting by Andrea Shalal; Editing by Mark Heinrich)