Turkish President Recep Tayyip Erdogan has suggested a fresh summit between himself and the leaders of Russia, France and Germany to discuss the situation in the Syrian rebel stronghold of Idlib, Russian media reported.

After a meeting with Russian President Vladimir Putin on the sidelines of the G20 summit in Buenos Aires on Saturday, Erdogan said the pair had discussed Syria and that it would be "right" to hold another summit, according to the TASS news agency.

Erdogan, Putin, German Chancellor Angela Merkel and French President Emmanuel Macron previously met in Istanbul in October in a bid to relaunch a peace process to end Syria's seven-year civil war.

Idlib is the rebels' last stronghold. In September Russia and Turkey reached a deal to establish a demilitarized buffer zone in the enclave, a move that prevented a major government offensive there.

However militants have remained in the area despite an October 15 deadline to withdraw and shelling from both sides has continued.

Erdogan's meeting with Putin was the second between the two leaders in two weeks. The Russian leader was in Istanbul for a ceremony to mark the completion of a section of an offshore natural gas pipeline on November 19.

Their meeting on Saturday was extended after Putin was left with a hole in his schedule following US President Donald Trump's cancellation of their own meeting over Russia's seizing of Ukrainian ships last weekend.

Erdogan meanwhile spent 50 minutes with Trump, Turkish state news agency Anadolu reported, without giving any further details.

The Turkish president later told reporters that the pair had discussed issues including Syria and an anticipated fine against Turkish state-run lender Halkbank related to sanctions on Iran.

Global trade is getting “even more chaotic,” Erdogan said, adding that unilateral decisions by some countries were harming global institutions.

He refused to name any countries, though the United States under Trump has upset Turkey as well as China and traditional allies in Europe and North America by slapping tariffs on them.

“This year's G20 summit is being held at a time when we are discussing trade wars instead of cooperation in global economy,” Erdogan said.

The World Trade Organization had suffered “a serious erosion of principles,” Erdogan, stressing the need for structural reforms within the organization.

Turkey was one of eight countries to which Washington granted temporary waivers to continue importing Iranian oil as it reimposed sanctions on Iran last month.

Erdogan has rejected the sanctions as "disrupting the world's balance," according to Anadolu.