Germany and other western European powers need to work with Russia as well as the US to solve the crisis in Syria, German Chancellor Angela Merkel said on Saturday.

Russia had earlier called for cooperation with the United States to avoid "unintended incidents", as it stages naval exercises off the coast of Syria, where U.S. officials believe Moscow is building up forces to protect long-term ally President Bashar al-Assad.

Syrian state media said on Saturday two Russian planes carrying 80 tonnes of humanitarian aid arrived in Syria. Russia said on Friday it had been sending military equipment to help the Syrian government fight Islamic State.

Chancellor Angela Merkel said more cooperation with Moscow is needed to find a political solution to the crisis in Syria. AP

In an interview with regional German newspapers, German Foreign Minister Frank-Walter Steinmeier warned Russia against going it alone in Syria, saying: "I hope that Russia is not depending on the Syrian civil war continuing."

Separately in a guest article for the New York Times, Steinmeier said the nuclear deal struck between Iran and six world powers had created an opportunity to tackle Syria's troubles, but said he was concerned that the chance to make progress was fading.