WASHINGTON: Looming across-the-board budget cuts will present the US military with the most significant readiness crisis in more than a decade unless quick action is taken to avoid the spending reductions, Defense Secretary Leon Panetta warned during testimony Thursday before the Senate Armed Services Committee.    

If the billions of dollars in cuts are allowed to stand, Panetta said, he would have to throw the country's national defense strategy ''out the window,'' and the United States would no longer be a first-rate power.

''This will badly damage our national defense and compromise our ability to respond to crises in a dangerous world,'' Panetta said. Anticipating the Defense Department will have less money to spend, Panetta said the Pentagon has already put in place a freeze on hiring and cut back on maintenance at bases and facilities.

Those moves are reversible, he said, as long as Congress acts quickly to head off the cuts, known as sequestration, and approves a 2013 military budget.

Panetta, who is retiring soon from his post, has been leading a vocal campaign to stop sequestration because it would leave the military ''hollow,'' meaning the armed forces would look good on paper but would lack the training and equipment they need to handle their missions.

As part of that campaign, the Defense Department has been providing greater details on the impact of the cuts. The department on Wednesday said it is cutting its aircraft carrier presence in the Gulf region from two carriers to one, a move that represents one of the most significant effects of the spending cuts.

The US has maintained two aircraft carrier groups in the Gulf for much of the last two years.

The potential for sequestration is a result of Congress' failure to cut the deficit by $1.2 trillion over a decade.

The Pentagon faces a $42.7 billion budget cut in the seven months starting in March and ending in September.

Congress has not approved a defense budget for the 2013 fiscal year. Lawmakers have instead been passing bills to keep spending levels at the same rate as last year.

That means the Pentagon is operating on less money than it planned for, and that compounds the problem, Panetta said.

''We have got to end the cloud of budget uncertainty that hangs over the Department of Defense and the entire US government,'' Panetta said.