WASHINGTON, July 2: Opening up a third front would pose a challenge for the US military already deployed in Iraq and Afghanistan, a top US military chief said on Wednesday amid concerns Israel may attack Iran.

“From the US military perspective, opening up a third front right now would be extremely stressful on us,” the Joint Chiefs of Staff Admiral Michael Mullen told a press conference.

“That doesn’t mean we don’t have capacity or reserve. But that would really be very challenging and also the consequences of that sometimes are very difficult to predict.”

Tel Aviv has said it will stop Tehran developing a nuclear bomb at all costs, amid speculation that it is seeking Washington’s tacit approval for a strike against Tehran’s atomic program.

The US army is already stretched with thousands of troops committed to fighting in Afghanistan and Iraq.

Admiral Mullen, who has just returned from a visit to Israel, refused to comment on what the US ally might be planning.

“But I’m convinced that the solution still lies in using other elements of national power to change Iranian behaviour, include diplomatic, financial and international pressure.

“There is a need for better clarity, even dialogue at some level.”

Bush urges diplomatic solution: Meanwhile, President George Bush on Wednesday sought to tamp down speculation that Israel will launch a military strike against Iran before he leaves office. He said all options are on the table but military action would not be his first choice.

“I have made it very clear to all parties that the first option ought to be solve this problem diplomatically,” Bush said at a White House news conference. “And the best way to solve it diplomatically is for the United States to work with other nations to send a focused message — and that is, you will be isolated, and you will have economic hardship if you continue to enrich.”

Iran says its nuclear program is aimed only at generating electricity and cites its right under the Nuclear Non-Proliferation Treaty to pursue uranium enrichment, a process that can produce either fuel for a nuclear reactor or material for a warhead.The United Nations has demanded Iran suspend enrichment and has imposed three rounds of similar financial sanctions on Iranian companies and individuals. The United States and European allies have been pushing Iran to halt enrichment and offering incentives, to no avail.

Bush also said it has been a “tough month” in Afghanistan, where more US and Nato troops died during the past two months than in Iraq. He said he was weighing whether to send more US troops to Afghanistan.

The president said that one reason for the rising deaths “is that our troops are taking the fight to a tough enemy...of course there is going to be resistance.” It has also been a “tough month for the Taliban,” he said.

Bush spoke ahead of a trip to Japan this weekend to participate in the annual Group of Eight economic summit.

In June, militants killed more US and Nato troops in Afghanistan than in Iraq for the second straight month. It was the deadliest month for US troops in Afghanistan since the war began.

Asked whether he might send more troops before 2009, Bush said: “We’re constantly reviewing troop needs, troop levels.”

Bush outlined his goals for his last G-8 summit of nations, which are the United States, Britain, Canada, France, Germany, Italy, Japan and Russia.

The debate about what to do about global warming will be front and center in Hokkaido too, although the discussion will be on the sidelines of the actual summit. Bush is hosting a meeting of major economies to urge nations to embrace long-term commitments to reduce green house gas emissions, but he appeared to be lowering expectations.

“The first step is to agree to a long-term goal,” Bush said, adding that his advisers think other nations are “now coming to that clear understanding that we’re going to have to come to a long-term goal. Hopefully, we can do it at this meeting. If not, we’ll continue to press forward to get it done.”

Bush also said Congress was in part to blame for rising gas prices that have stung American consumers.

He said lawmakers continue to block his proposals, including lifting prohibitions on offshore oil drilling.

The president has also called for allowing oil drilling in a portion of the Arctic National Wildlife Refuge for drilling, easing the regulatory process to expand oil refining capacity, and lifting restrictions on oil shale leasing in three western states. —Agencies