Nearing a decision on sending more troops off to war, President Obama told a military audience Thursday that he will not dispatch them into conflict without proper support -- including the backing of the American people.

"That is a promise that I make to you," Obama told more than 1,000 troops and their families gathered at a hangar here, as the president stopped briefly for refueling en route to a four-country trip to Asia.

The president made no direct mention of Afghanistan or his weekslong review, now nearing completion, of how to revamp the struggling war effort there. Obama is expected to send in thousands more troops.

In recent days, from a somber memorial for the 13 people shot to death at Fort Hood in Texas to a Veterans Day ceremony at Arlington National Cemetery, Obama has lauded the determination of the all-volunteer military.

But his assurance Thursday about public support was new, and it was unclear how he would rally it.

An Associated Press-GfK poll this week showed that 48 percent of people disapprove of Obama's handling of Afghanistan, up from 41 percent in October. More than half of all Americans -- 54 percent -- now oppose sending more troops to Afghanistan, an increase from 50 percent last month.

"I want you guys to understand that I will never hesitate to use force to protect the American people and our vital interests," Obama told the troops. "But I also make you this promise: I will not risk your lives unless it is necessary to America's vital interests."

"And if it is necessary," Obama added, "the United States of America will have your back. We'll give you the strategy and the clear mission you deserve. We'll give you the equipment and support you need to get the job done. And that includes public support back home."