By Susan Cornwell and Caren Bohan
WASHINGTON (Reuters) - Senior U.S. officials on Wednesday stressed the diplomatic and military risks of imposing a "no-fly" zone over Libya to help rebels fighting Muammar Gaddafi's forces, saying such a move was not imminent.
Some U.S. lawmakers have urged a no-fly zone as a way to loosen Gaddafi's grip on power but opposition is high among Arab nations to any foreign intervention and Washington has stressed the need to work with allies to resolve the crisis.
"Let's just call a spade a spade. A no-fly zone begins with an attack on Libya to destroy the air defenses," Defense Secretary Robert Gates told a budget hearing in the House of Representatives. "And then you can fly planes around the country and not worry about our guys being shot down."
U.S. officials say all options are on the table over the violence in the oil-producing North African nation. But they are wary of military steps as they grapple with the financial and human costs of long, bloody wars in Iraq and Afghanistan.
Secretary of State Hillary Clinton, who just returned from a consensus-building trip to Geneva, said U.S. military assets could be used to support the movement of supplies to Libyan areas in need but a no-fly zone was not an immediate priority.
"I think we are a long way from making that decision," Clinton told a Senate hearing. "There is a great deal of caution that is being exercised with respect to any action we might take other than in support of humanitarian missions."
In a symbolic show of force aimed at keeping pressure on Gaddafi, the United States sent warships toward Libya. Two amphibious assault ships, the USS Kearsarge and the USS Ponce, are now in the Mediterranean Sea, a U.S. official said.
The United States also has an aircraft carrier, the USS Enterprise, in the Red Sea but military officials have not said whether it will be sent to the Mediterranean.
MONITORING OIL PRICES
Gaddafi launched a land and air offensive on Wednesday to retake territory in eastern Libya, prompting a group of rebels to call for U.N.-backed air strikes on African mercenaries helping him stay in power.
Airstrikes by Libyan forces in Brega, near an oil terminal, pushed oil prices to 2-1/2-year-highs as investors worried about the potential spread of instability to other producers in the region.
U.S. crude oil futures surged above $102 a barrel, closing at their highest level since September 2008.
"We are closely monitoring the situation," White House spokesman Jay Carney said. "The president is extremely aware of the impact a spike in oil prices can have on gasoline prices and therefore on the wallets ... of average Americans."
Some Republicans have accused President Barack Obama of being too muted in his response to the turmoil sweeping North Africa and the Middle East.
Obama, seeking to push back on such criticisms, is crafting a broader strategy for the region and will roll it out in the coming weeks.
Clinton said one of the biggest U.S. concerns is "Libya descending into chaos and becoming a giant Somalia."
"It's right now not something that we see in the offing but many of the al Qaeda activists in Afghanistan and later in Iraq came from Libya and came from eastern Libya, which is now the so-called free area of Libya."
Two senior U.S. senators, John McCain and Joe Lieberman, called for a no-fly zone over Libya in an interview with Reuters on Tuesday.
"I believe that Gaddafi's days are numbered and we should do everything in our power to shorten the number of days so that we can relieve the misery of the people of Libya," McCain said.
McCain, a Republican, and Lieberman, an independent, just returned from a North Africa and Middle East tour where they spoke with leaders emerging from the upheavals in Egypt and Tunisia.
The Cairo-based Arab League, which has suspended Libya, said on Wednesday it could impose a no-fly zone in coordination with the African Union if fighting continued.
(Additional reporting by Andrew Quinn, Arshad Mohammed, Missy Ryan, Alister Bull and Ross Colvin; Writing by Caren Bohan; Editing by John O'Callaghan and Cynthia Osterman)