Turkey wants Mr. Assad gone, and has allowed its border with Syria to be an easy crossing point for Syrian rebels, including those the West regards as terrorists or radical Islamists; Russia wants to prop up Mr. Assad and his government. While Moscow says it is attacking the Islamic State, for the most part Russian planes and troops have been attacking the Syrian rebels, some of whom are supported by the United States and the West, who most threaten Mr. Assad’s rule.

Mr. Obama said again Tuesday that Russian air attacks on moderate opponents of Mr. Assad had only helped him and that they should be directed at the Islamic State.

Mr. Hollande and Mr. Obama clearly hoped that the bombing of a Russian passenger jet over Egypt, claimed by the Islamic State, would cause Moscow to make defeating the jihadists more of a priority than propping up Mr. Assad. But Tuesday’s events will make that a tougher sell, for President Vladimir V. Putin of Russia wants to be seen as an equal player in the conflict, not beholden to Western policies.

Turkey, especially under the increasingly authoritarian rule of its nationalist president, Recep Tayyip Erdogan, has been fierce in defending its airspace, shooting down Syrian jets that have strayed in the past. Turkey insisted that it issued 10 warnings over a five-minute period to the Russian pilot of the Sukhoi Su-24 to pull away.