WASHINGTON — Obama administration officials struggled Wednesday to clearly define for lawmakers what are "enduring offensive ground combat operations." But they did shed light on what it's not.

Those five words are part of a draft authorization for the use of military force (AUMF) the White House submitted to Congress last month. And in the weeks since, they have become five of the most confusing and contentious words on the American political landscape.

Joint Chiefs Chairman Gen. Martin Dempsey told the Senate Foreign Relations Committee that "enduring" is neither a word nor a concept etched in military doctrine.

At one point, Defense Secretary Ash Carter fielded a question on the definition from Sen. Time Kaine, D-Va., and began with a long, deep, "Uhh …"

Audience members in the packed hearing room chuckled.

Kaine asked Carter, Dempsey and Secretary of State John Kerry whether a seven-month ground operation involving hundred of thousands of American troops would meet the "enduring" threshold.

Carter replied the scale of that kind of operation "is not something we foresee." But he did not speak to whether an operation under that scenario would be legally covered by the White House's AUMF.

Kaine and panel Ranking Member Sen. Bob Menendez, D-N.J., expressed concern that the administration's authorization measure would leave open the possibility of what he called "ground-troop creep," meaning a steady increase of more and more US forces flowing into Iraq.

Kerry responded by saying the AUMF is crafted in a way to "guard against that." But he did not explain why.

The officials did clearly explain what the draft AUMF would not legally cover: a US ground operation with hundreds of thousands of American troops that spans more than a decade.

The authorization was crafted to prevent another post-9/11 operation like those in Iraq and Afghanistan, which experts say yielded questionable strategic returns for the United States.

President Barack Obama's envoy to the anti-Islamic State coalition, retired Marine Gen. John Allen, told lawmakers earlier this year that the five words could conceivably be used to legally justify an operation spanning two weeks or two years.

Kerry broke with Allen, telling the members he "disagrees."

Administration officials do not expect any single US ground operations to lasting multiple months or nor multiple years, the officials said.

Last week, Carter broke a bit from the White House over the three-year span of its proposed authorization measure.

"That is not something that I would have deduced from the Department of Defense's necessities, the campaign's necessities or our obligation to the troops," he told the House Appropriations Defense subcommittee.

But on Wednesday, Carter walked that back, telling the Senate committee he cannot tell lawmakers the US fight against the Islamic State will be over in three years. And he urged Congress to approve the administration's submission.

The wording has split Republicans and Democrats. The former believes it is too restrictive and the latter feels it is too vague.

Panel Chairman Sen. Bob Corker, R-Tenn., said he is unaware of a single Senate Democrat who supports the version crafted by the White House.

At the hearing's start, Kerry used some bravado-laced rhetoric, saying the Islamic State group "cannot defeat us."

Notably, Dempsey told the committee up to 20,000 Shiite militia members trained by Iran are fighting in Iraq.

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