Turkish President Recep Tayyip Erdogan says he'll resign if Moscow can prove its claim that Turkey shot down a Russian plane to protect its oil trade with ISIS.
"As soon as such a claim is proved, the nobility of our nation requires [me] to do this," Erdogan told reporters at the climate change summit in Paris on Monday.
But, he added, if the allegations are untrue, then Russian President Vladimir Putin should resign.
"I am asking Mr. Putin, would you remain?"
And so goes the escalating war of words between the two nations which began after Turkish aircraft shot down a Russian warplane near its border with Syria on November 24. The pilot died.
Turkey says the plane was in its airspace; Russia says it was bombing ISIS targets.
Putin: Defending airspace a pretext
On Monday, Putin alleged that downing the plane in the name of defending airspace was just a pretext.
"We have recently received additional reports that confirm that oil from ISIL-controlled territories is delivered to the territory of Turkey on an industrial scale," he said, according to TASS news agency. ISIS is also referred to as ISIL.
"We have all grounds to suspect that the decision to down our plane was motivated by the intention to secure these routes of delivering oil to ports where it is loaded on tankers," he said.
Untrue, Erdogan said.
"It is obvious where we legally buy oil and natural gas from," Erdogan said, as reported by Turkey's Anadolu news agency. "Everyone must know that we are not that disreputable to make such a deal with terrorist organizations."
Taking Turkey's side
In the bitter debate over where the Russian warplane was flying when it was shot down, the United States took Turkey's side Monday.
The available information indicates the warplane was in Turkish airspace, State Department spokeswoman Elizabeth Trudeau said.
Also Monday, the body of the Russian pilot, Col. Oleg Peshkov, was flown back to Russia.
Tensions rise as Russia says it's deploying anti-aircraft missiles to Syria.