* U.S. has urged Israel not to attack Iran but give diplomacy more time
* Netanyahu's remarks signal growing impatience
* Israel wants stronger language from Obama, says Iran pushing ahead
* Iranian general: Israeli officials would be targets if Israel attacked Iran
By Jeffrey Heller
JERUSALEM, Sept 2 (Reuters) - Israeli Prime Minister Benjamin Netanyahu urged world powers on Sunday to set a "clear red line" for Tehran's atomic activities and said they had failed to convince it of their resolve to prevent Iran from obtaining nuclear arms.
Netanyahu's remarks suggested a growing Israeli impatience with its main ally, the United States, and other countries that have been pressing him to give diplomacy and sanctions more time to work and hold off on any go-it-alone Israeli strike on Iran.
"I believe the truth must be stated: The international community is not placing a clear red line for Iran and Iran does not see international resolve to stop its nuclear programme," Netanyahu told his cabinet.
"Unless Iran sees this clear red line and this clear resolve it will not stop moving forward with its nuclear programme, and Iran must not have nuclear weapons," he said in broadcast remarks.
Although Netanyahu did not single out the United States or U.S. President Barack Obama in his criticism, Israeli officials have said they hope for stronger language from the president about possible U.S. military action.
Obama, who has had a frosty relationship with Netanyahu, has insisted he will not allow Iran to build atomic weapons and that all options are on the table.
On Saturday Tzachi Hanegbi, an influential former Israeli legislator and a Netanyahu confidant, said "the rhetoric of the U.S. president is too vague, very amorphous" and Iran was not taking Obama's words seriously.
In a U.S. election year, Republican candidate Mitt Romney has also sharply criticised Obama's handling of Iran as not being tough enough.
Tehran says it is refining uranium to fuel a planned network of nuclear power plants so that it can export more of its oil and gas. The United States and its allies accuse Iran of a covert bid to develop the capability to make nuclear bombs.
Israel, believed to have the only nuclear arsenal in the Middle East, views a nuclear-armed Iran as a threat to its existence.
Netanyahu has said he will speak out about the dangers of Iran in an address this month to the U.N. General Assembly in New York. He is also expected to hold talks with Obama during his visit, but no announcement has yet been made.
A senior Israeli official told Reuters last week Netanyahu would seek a firm pledge of U.S. military action if Iran did not back down on uranium enrichment. Such a promise could dissuade Israel from attacking Iran alone, Israeli officials have said.
A United Nations report said on Thursday that Iran had more than doubled the number of centrifuges in its fortified bunker at Fordow since May, showing it was still expanding its nuclear programme despite Western pressure and threat of Israeli attack. The new machines are not yet operating, the report said.
"The report confirms what I have been saying for a long time, international sanctions are a burden on Iran's economy but they are not in any way delaying the advancement of Iran's nuclear programme," Netanyahu told his cabinet, in public remarks opening the meeting.
"The Iranians are using the talks with the world powers to win time and to advance their nuclear programme," he said.
General Martin Dempsey, chairman of the U.S. joint chiefs of staff, has suggested Washington would not be drawn into conflict with Iran should Israel attack. "I don't want to be complicit if they (Israel) choose to do it," Britain's Guardian newspaper quoted him on Friday as saying.
Recent heightened Israeli rhetoric has stoked speculation that Israel might attack Iran before the U.S. elections in November, believing that Obama would give it military help and not risk alienating pro-Israeli voters.
Israeli officials have said Israel has yet to decide, amid divisions within its security cabinet and warnings by military and security chiefs that a strike would have only a limited effect in setting back Iran's nuclear programme.
An Iranian general said that if Israel were to attack Iran, Israeli officials would be the target of retaliation, Iranian media reported on Sunday.
"In case of Israel's military attack against Iran, the officials of (Israel) will be among the first victims of such an attack," Mohammad Ali Assoudi, a brigadier general in the Islamic Revolutionary Guard Corps, told Iran's English-language Press TV.
His broadcast remarks gave no details, but Press TV paraphrased him as saying Israel's policies had induced hatred of its officials among residents of the occupied territories.
Iran has undertaken large-scale military manoeuvres this summer and unveiled upgrades to weapons it says are defensive, including what it said was a more accurate short-range missile.