* World powers share "common concern" about Iran -envoy
* Says Israel can't be blamed for Iran's nuclear program (Updates with additional quotes, background)
By Louis Charbonneau
NEW YORK, Feb 11 (Reuters) - World powers discussing possible new sanctions against Iran over its nuclear program should take as much time as necessary to secure China's backing, France's U.N. ambassador said on Thursday.
"It's totally essential to work with the Chinese, even if it means waiting a bit," French envoy Gerard Araud told an audience of academics, students and diplomats at New York's Columbia University.
He declined to provide any details on negotiations on a fourth round of U.N. sanctions against Tehran currently underway among the United States, France, Britain, Germany, Russia and China.
Unlike Russia, China has indicated that it is very reluctant to pursue new sanctions against Tehran, with which both Beijing and Moscow have close economic ties.
Araud added that Russia and China had supported three Iran sanctions resolutions and were committed to tackling Iran and its defiance of five Security Council resolutions demanding that Tehran halt its nuclear enrichment program.
"I wouldn't consider dumping China," he said.
Araud acknowledged that the five veto-wielding permanent U.N. Security Council members and Germany did not always share the same views on the best strategy for dealing with Iran.
"Of course there are nuances between the members," he said, adding that what bound them together was their shared concern about Tehran's nuclear program.
"This common concern is still there," he said.
Western diplomats on the Security Council say that the United States, Britain, France and Germany hope to have an agreement with Russia and China on the basic elements for a new sanctions resolution by the end of this month so that the 15-nation council could vote on it by the end of March.
But such a timetable is highly ambitious given China's reluctance to take further punitive steps against Iran.
Iran, a major oil and gas producer, rejects Western allegations that it is secretly developing nuclear weapons. It insists that its nuclear ambitions are limited to the peaceful generation of electricity.
Among the ideas that the United States and France have floated in informal papers, the contents of which were described to Reuters by several diplomats, are expanding U.N. travel bans and asset freezes to include members of Iran's Islamic Revolutionary Guard Corps and firms owned by it.
They also hope to blacklist Iran's central bank and other financial institutions suspected of financing the Islamic Republic's nuclear and missile programs. France's paper suggests targeting Iran's energy sector, a punitive measure that was not included in the U.S. paper, diplomats said.
Asked what would happen if the international community failed to persuade Iran not to develop atomic weapons, Araud made clear that Israel might decide to use force.
"Failure would be extremely serious," he said. "There is a risk of military confrontation."
He added that a Middle East nuclear arms race could be sparked and a "collapse of the Non-Proliferation Treaty" might result.
Iran is a signatory of the NPT.
The French envoy also rejected the idea that Israel's presumed nuclear arsenal had played any role in Iran's decision to pursue a covert atomic program.
"Israel has nothing to do with the Iranian nuclear program," he said, adding that Iranian President Mahmoud Ahmadinejad's threatening remarks about the Jewish state were "a smoke screen."
Israel neither confirms nor denies having a nuclear arsenal though analysts estimate that it has a triple-digit stockpile of atomic weapons. (Editing by Eric Beech)