* U.S. official says talks could resume at some point
* France says 5+1 united, ready to apply more pressure
* Israel draws "red line" over Iran nuclear program
By John Irish
NEW YORK, Sept 27 (Reuters) - China said on Thursday that the disagreement over Iran's nuclear program had reached "a new, crucial stage," calling for Tehran to begin a new round of talks with world powers, something a U.S. official said could happen at some point.
Chinese Foreign Minister Yang Jiechi made the comment after Israeli Prime Minister Benjamin Netanyahu made a speech drawing a "red line" for Iran's nuclear program on Thursday, despite a U.S. refusal to set an ultimatum, saying Tehran will be on the brink of a nuclear weapon in less than a year.
While Netanyahu was not entirely clear on the point, he appeared to suggest that if Iran were to acquire enough 20 percent enriched uranium needed for a single bomb, it would have crossed his proposed "red line" and could face military action.
Yang spoke several hours after Netanyahu's U.N. General Assembly address and after a meeting of officials from the five permanent members of the U.N. Security Council - the United States, France, Britain, Russia and China - and Germany yielded no obvious signs of progress toward a diplomatic solution.
"The Iranian nuclear issue has reached a new, crucial stage," Yang said in a speech at the U.N. General Assembly. "The relevant parties should remain committed to a diplomatic solution and begin a new round of dialogue as soon as possible."
A senior U.S. official said "at some point" the group would likely return for a fourth round of talks with Iran.
"I think we've got some additional work to do first, so I would not expect that to happen immediately, but I would hope that we will get there in the not-too-distant future," said the official, who spoke on condition of anonymity.
The push to resume talks comes at a time when tensions between Iran and Israel are rising and diplomatic efforts to resolve the decade-long dispute over Iran's nuclear work have foundered.
Israel, the United States, the European Union and their allies say Iran is amassing the capability to produce a nuclear bomb, an allegation the Islamic Republic denies.
The six world powers, represented by EU foreign policy chief Catherine Ashton, have sought to persuade Iran to scale back the enrichment of uranium through intensifying economic sanctions and diplomacy.
France said earlier this week it would seek a new round of EU sanctions targeting Iran's financial sector next month. Foreign Minister Laurent Fabius said after Thursday's talks the group was "united" and ready to apply more pressure on Tehran.
They have so far failed to reach a breakthrough in three rounds of talks since April.
Western sanctions on Iran tightened markedly this year with an EU ban on crude oil purchases from Iran and U.S. sanctions targeting banks that deal with Iran's central bank.
U.N. diplomats say the possibility of further U.N. Security Council sanctions is slim because Russia and China are opposed to the idea. There was no sign the issue was discussed on Thursday.
After the talks on the sidelines of the U.N. General Assembly in New York, Ashton said the powers had discussed the need for Iran to take action urgently regarding its nuclear issue and planned to contact Tehran to continue the process.
"We have to ensure that we aren't going to have talks for talks' sake, and we have some reason to believe that they will move to a point of seriousness, but we will test this out every step of the way," the U.S. official said.