Turkish President Recep Tayyip Erdogan said Monday that he would resign if Russia could prove that Turkey shot down a Russian warplane near the Syrian border in order to protect its oil trade with Islamic State.Erdogan's comments, made to reporters at the UN climate summit in Paris, came in response to allegations made by Russian President Vladimir Putin on Monday.Putin, who has signed a decree imposing economic sanctions on Turkey over the incident, said on Monday Turkey shot down the Russian jet because it wanted to protect supplies of oil from Islamic State militants."As soon as such a claim is proved, the nobility of our nation requires [me] to do this," CNN quoted Erdogan as telling reporters at the climate change summit in Paris on Monday. Erdogan added, however, that should the claims prove to be false, Putin should be the one to step down.Turkish Prime Minister Ahmet Davutoglu called on Tuesday for the opening of communication channels between Turkey and Russia to prevent incidents like the downing of a Russian warplane by Turkish jets along the Syrian border last week.Putin and Erdogan did not meet at Monday's summit in Paris which Erdogan had described as an opportunity to mend shattered ties between the two countries. "Our call to Russia again is to open military communication channels to prevent similar incidents happening. Let's keep diplomatic channels open," Davutoglu told a news conference before departing on an official visit to northern Cyprus."We must sit down and talk at the table instead of making unfounded allegations," he added.Davutoglu said Turkey will continue in its efforts to expel Islamic State militants from the area on the Syrian side of the border between the two countries.Meanwhile, US President Barack Obama urged his Turkish counterpart on Tuesday to reduce tensions with Russia while stressing US support for its NATO ally's security.Obama met Erdogan in Paris, where he has been attending the climate summit."The United States supports Turkey's right to defend itself and its air space ... We discussed how Turkey and Russia can work together to deescalate tensions" and find a diplomatic path to resolve the issue," Obama said.Obama said he stressed to Erdogan that the Islamic State militant group was the enemy that all sides needed to focus on.