The U.N. Security Council approved a new round of sanctions targeting Iran's nuclear program on Wednesday, sending an "unmistakable message" that Tehran must fulfill its obligations under the nuclear Nonproliferation Treaty (NPT), President Obama said after the vote.

Leaders of Russia, Turkey and Iran convened at a security summit meeting in Istanbul on Tuesday in a display of regional power that appeared to be calculated to test the United States just days before a scheduled American-backed debate in the United Nations Security Council on imposing tighter sanctions over Iran’s nuclear program.