"Let me say this, according to information I received from my intelligence chief, neither of the sides will use nuclear weapons as of now," Erdogan was quoted as telling journalists in Indonesia where he attended the G20 summit.

The US and Russian spy chiefs held a rare face-to-face meeting in Ankara on Monday on Moscow's nuclear threats in Ukraine and Americans held by the Kremlin, the White House said.

In what appeared to be the highest-level direct talks between officials of the two countries since Russia invaded Ukraine in February, Central Intelligence Agency Director William Burns met with Sergei Naryshkin, head of Russia's SVR foreign intelligence service.

Erdogan said he wanted to keep both sides in close dialogue.

"Of course we want them ... to come together often," he said.

"God forbid, (use of nuclear weapons) could lead to a new world war. Let's not let that happen," he added.

The United States has warned for months over Russian threats to use tactical nuclear weapons in Ukraine if its own territorial integrity was threatened.