Donald Trump's election as US president could provide fresh momentum for ending Syria's six-year-old civil war, the president of the opposition Syrian National Coalition (SNC) said on Wednesday.

Speaking to Reuters, coalition president Anas al-Abdah also urged Germany to step up its efforts to end the war and push for limited sanctions against Russia for its support of President Bashar al-Assad.

"The new (US) president-elect has the will and the leadership to reassert American leadership in the area and in Syria," he said in an interview, contrasting this with the current US approach which he said had allowed Russia to act with impunity.

The Turkey-based SNC is a coalition of political and rebel groups which is backed by Western countries that oppose Assad.

One insurgent group on the ground in Syria was less optimistic.

"I think things will become difficult because of Trump's statements and his relationship with Putin and Russia. I imagine this is not good for the Syrian issue," Zakaria Malahifji, head of the political office of an Aleppo-based rebel group, told Reuters earlier on Wednesday.

Trump is widely viewed as having a more open-minded stance towards Russia than the current US administration, triggering concerns that this could embolden Russia. President Vladimir Putin said following Trump's election win that Moscow was ready to do its part to fully restore ties with Washington.

Al-Abdah said the SNC had sent Trump its congratulations and was in touch with a Trump adviser about a comprehensive new approach to Syria.

Once the incoming Trump administration got engaged, it would also be important for Europe to present a unified view, he said.

He said SNC officials discussed a range of next steps with German Foreign Minister Frank-Walter Steinmeier on Wednesday, including imposition of limited sanctions against Russian companies and banks that are aiding Assad and limited military strikes.

Al-Abdah said Steinmeier had promised to do all he could to end the targeting of Syrian civilians, and told the opposition officials he would convene a meeting in coming days of European Union officials to discuss Trump's victory and the consequences for Syria.

No comment was immediately available from the foreign ministry.

Syrian opposition officials said they sensed growing German interest in limited sanctions.

"It's time for Germany to lead European foreign policy in many areas, but specifically with regard to Syria," al-Abdah said.

Germany had the respect of its EU counterparts and a certain "moral authority" since it accepted the largest number of Syrian refugees over the past two years, and enjoyed good relations with both Russia and the United States.

"They can bring some new sanity into this discussion," al-Abdah said. "The monopoly between the US and Russia has not really produced any good results so far."