Updated at 12:45 p.m., ET: WASHINGTON -- A 30,000-pound bunker buster bomb designed to smash through some 200 feet of concrete before exploding is a "great weapon" that could be used by U.S. forces in a clash with Iran over its nuclear program, an Air Force general said on Thursday.
Israel stepped in line, asking the United States for the advanced bombs and refueling planes that could aid an Israeli strike on Tehran's underground nuclear sites, an Israeli official told Reuters on Thursday.
"Such a request was made" around the time of Israeli Prime Minister Benjamin Netanyahu's visit to Washington this week, the official said, confirming media reports.
But the official, who spoke on condition of anonymity given the sensitivity of the issue, played down as "unrealistic" reports that the United States would condition supplying the hardware on Israel promising not to attack Iran this year.
Netanyahu told President Barack Obama at a White House meeting on Monday that Israel had not yet decided on military action against Iran, sources close to the talks said.
'A great weapon'
Serious talk of the buster bomb surfaced on Thursday after a high-raking military official described the bomb, designed to smash through some 200 feet of concrete before exploding, as a "great weapon” and could be used by U.S. forces in a clash with Tehran over its nuclear program.
Lieutenant General Herbert Carlisle, Air Force deputy chief of staff for operations, said the massive ordnance penetrator, which the military began receiving only last year, is part of the U.S. arsenal available for strikes against countries like Iran, which has some buried nuclear facilities.
"The massive ordnance penetrator is a great weapon. We are continuing to improve that. It has great capability now and we are continuing to make it better. It is part of our arsenal and it will be a potential if we need it in that kind of scenario," Carlisle told a conference on U.S. defense programs.
The Pentagon has begun working on military options if sanctions and diplomacy fail to prevent Tehran from building a nuclear weapon.
Defense Secretary Leon Panetta told the National Journal in an interview on Thursday that planning had been going on "for a long time."
Major powers are increasingly concerned about Iran's nuclear enrichment program, which they view as an attempt to build an atomic weapon. But Tehran says it is meant for peaceful energy production.
Israel holding off?
Israel is worried about potential for Iran to acquire nuclear weapons. Netanyahu said during his Washington visit that time was running out for diplomacy and sanctions.
Nevertheless, Netanyahu reportedly is willing to wait at least a few weeks to let sanctions work.
"I am not standing with a stopwatch in hand. It is not a matter days or weeks, but also not a matter of years. Everybody understands this," Netanyahu told an news program in Israel according to Britain's Telegraph newspaper.
NBC News' Richard Engel and the Carnegie Endowment's Karim Sadjadpour join Morning Joe to discuss why the most important thing for the current Iranian regime is "to stay in power" and why the Ahmadinejad regime is not a suicidal regime.
"We would be happy if this thing is resolved peacefully, if Iran decides to stop its nuclear program," he said according to the Telegraph. "To stop it, to dismantle its facility in Qom, and to stop enriching uranium. I will be most happy, I think all Israel's citizens will also be happy."
Panetta, who has said diplomacy and sanctions should be given more time, told the National Journal he did not think Israel had decided whether to order a high-risk raid on Iran's nuclear sites.
He said the United States was committed to preventing Iran from acquiring atomic weapons and would have a greater impact than Israel if it decided force was necessary.
"If they decided to do it there's no question that it would have an impact, but I think it's also clear that if the United States did it we would have a hell of a bigger impact," Panetta said.
The tough rhetoric from the Pentagon came despite President Barack Obama's effort this week to tamp down "loose talk" and "bluster" about possible military action, saying there was still an opportunity for diplomacy.
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Reuters and msnbc.com staff contributed to this report.