U.S. President Barack Obama and Russian President Vladimir Putin will meet in New York next week at a time of high tension in Europe and the Middle East, but the Kremlin and the White House differed on Thursday over the top priority for the talks.

The White House said the main issue for talks would be the conflict in eastern Ukraine, where Russian-backed forces are fighting the Kiev government, prompting tough sanctions that have damaged Russia's economy.

The Kremlin in Moscow, however, said the main focus would be on Syria, where Russia has built up its military forces in recent weeks with combat aircraft, tanks and other equipment in support of President Bashar Assad.

Putin's spokesman, Dmitry Peskov, told reporters: "Of course, the primary topic will be Syria."

Asked whether Ukraine would be discussed, he said: "Well, if time allows."

Both leaders will be in New York to address the United Nations General Assembly on Monday morning. Peskov said the meeting would take place after Putin's speech.

The two camps also differed over who called for the meeting. White House spokesman Josh Earnest said it was being held at Putin's request, but the Kremlin said it was organized "by mutual agreement."