U.S. President Barack Obama says Iran could face much stronger international sanctions if it keeps pursuing nuclear weapons.

Mr. Obama said after White House talks with Israeli Prime Minister Benjamin Netanyahu Monday that a nuclear-armed Iran would threaten not just Israel and the United States, but the whole world.

Mr. Obama described Iran as a country of "extraordinary history and potential."  He said he is reaching out to the Iranian government to convince it that building nuclear bombs is not in its interests.

But the president said he is giving diplomatic efforts with Iran until the end of the year to show results, saying talks cannot last forever.

Mr. Netanyahu said Iran openly calls for Israel's destruction, something he termed unacceptable. The Israeli prime minister said if Iran were to acquire nuclear weapons, it would give a nuclear umbrella to terrorists.

Mr. Obama earlier told Newsweek magazine that he wants to shift U.S. policy on Iran after 30 years of an old policy that has produced no results.

Iran's ISNA news agency quoted a foreign ministry spokesman as saying Mr. Obama's approach is realistic. He said the president should be given a chance to carry out his promise.

Israel and the United States accuse Iran of seeking to build nuclear weapons. Iran insists its nuclear program is peaceful.

Some information for this report was provided by AP and Reuters.