Retired General Anthony Zinni, the former head of US Central Command, told US television Sunday that he had no detailed knowledge of the alleged military plans, but he suggested a preemptive strike against Iran's nuclear program would be extremely risky.

"Any military plan involving Iran is going to be very difficult. We should not fool ourselves to think it will just be a strike and then it will be over," said Zinni.

"The Iranians will retaliate, and they have many possibilities in an area where there are many vulnerabilities, from our troop positions to the oil and gas in the region that can be interrupted, to attacks on Israel, to the conduct of terrorism," he said.

Zinni made his remarks after the publication of a pair of reports this weekend saying that the administration is seriously considering military action against Iran, amid a stalemate in diplomatic efforts.

The New Yorker magazine reported in its April 17 issue that the administration is planning a massive bombing campaign against Iran, including use of bunker-buster nuclear bombs to destroy a key suspected Iranian nuclear weapons facility.

The article by investigative journalist Seymour Hersh said that Bush and others in the White House have come to view Iranian President Mahmoud Ahmadinejad as a potential "Adolf Hitler."

"That's the name they're using," Hersh quoted a former senior intelligence official as saying.

Democratic Senator John Kerry, one of the administration's most outspoken critics, assailed the White House for being unable to deftly use international diplomacy as a political tool, and for a too-ready reliance on military might.

"That is another example of the shoot-from-the-hip, cowboy diplomacy of this administration.

"For us to think about exploding tactical nuclear weapons in some way is the height of irresponsibility. It would be destructive to any non-proliferation efforts and the military assessment is, it would not work," he told NBC television's "Meet the Press" program.

"What you really need here is China and Russia to join with the United States and others in serious sanctions," the former Democratic presidential contender said.

Meanwhile, according to a report Sunday in the Washington Post, Bush is studying options for military strikes against Iran as part of a broader strategy of coercive diplomacy to pressure Tehran to abandon its alleged nuclear program.

Citing unnamed US officials and independent analysts, the newspaper said no attack appears likely in the short term, but officials are preparing for it as a possible future option and are using the threat to convince Iranians of the seriousness of its intentions.

The paper said Bush views Tehran as a serious menace that must be dealt with before his presidency ends, and the White House, in its new National Security Strategy, labeled Iran the most serious challenge to the United States posed by any country.

Zinni said he shared Washington's concerns about Tehran's motives, but said diplomatic efforts should first be exhausted.

"I believe that if the international community would stand fast, the Russians and the Chinese would stay with us, I think that kind of pressure, the fear of being isolated and condemned as a rogue state could have the effect that we need to halt the program.

"I'm not saying that there isn't a military action that will become necessary at some point," Zinni continued.

"But I believe ... when you take that military action, you have to ask the question, 'and then what?' Because you're going to have a series of those 'and then whats' down the road," he said.

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