LONDON/WASHINGTON — U.S. Central Intelligence Agency Director William Burns is in Turkey to deliver a message to President Vladimir Putin's foreign spy chief about the consequences of a potential Russian use of nuclear weapons, a White House spokesperson said.

In the first known high-level face-to-face U.S.-Russian contact since Putin's Feb. 24 invasion of Ukraine, Burns was in Ankara on Monday to meet Sergei Naryshkin, head of Russia's SVR foreign intelligence service.

"He is not conducting negotiations of any kind. He is not discussing settlement of the war in Ukraine," said the spokesperson, speaking on condition of anonymity.

"He is conveying a message on the consequences of the use of nuclear weapons by Russia, and the risks of escalation to strategic stability," the spokesperson said. "He will also raise the cases of unjustly detained US citizens."

Burns, a former U.S. ambassador to Russia who was sent to Moscow in late 2021 by U.S. President Joe Biden to caution Putin about the troop buildup around Ukraine, is not discussing a potential settlement to the war in Ukraine, the spokesperson said.

"We briefed Ukraine in advance on his trip. We firmly stick to our fundamental principle: nothing about Ukraine without Ukraine."

Putin has repeatedly said Russia will defend its territory with all available means, including nuclear weapons, if attacked. Putin says the West has engaged in nuclear blackmail against Russia.

The remarks raised particular concern in the West after Moscow declared in September that it had annexed four Ukrainian regions that its forces control parts of.

The U.S.-Russian contact in Turkey was first reported by Russia's Kommersant newspaper. The Kremlin, asked about the Kommersant report, said it could neither confirm nor deny it. The SVR did not respond to a request for comment.

Beyond the war, Russia and the United States have a host of outstanding issues to discuss, ranging from the extension of a key nuclear arms reduction treaty and a Black Sea grain deal to a possible U.S.-Russian prisoner swap and the Syrian civil war.

U.N. Secretary-General Antonio Guterres, asked at a summit of the Group of 20 (G-20) leading economies in Indonesia about the U.S.-Russian contact in Turkey, said the United Nations was not involved.

"It's very positive that the U.S. and Russia are having talks because that is an extremely relevant development in relation to the future, but we are not involved," Guterres said.

Biden said this month he hoped Putin would be willing to discuss seriously a possible prisoner swap to secure the release of U.S. basketball star Brittney Griner, who was sentenced to nine years in a Russian penal colony on drugs charges.

Former U.S. Marine Paul Whelan, who holds American, British, Canadian and Irish passports, was sentenced in 2020 to 16 years in a Russian jail after being convicted of spying. He denied the charge.

Viktor Bout, a Russian arms dealer jailed in the United States, has been mentioned as a person who could be swapped for Griner and Whelan in any future prisoner exchange.

Kremlin says grain talks with U.N. last week were 'constructive.’

Biden expects Russia to get more serious about prisoner swap for Griner.