Forward Operating Base Walton, Afghanistan ? A soon-to-begin U.S. troop withdrawal from Afghanistan should leave combat power intact as long as possible to press an anti-Taliban offensive, U.S. Defense Secretary Robert Gates said Sunday. He said support troops should go first.

On his final trip to assess a war in its 10th year, Gates told soldiers the endgame in Afghanistan is more likely to turn out well if the drawdown promised by President Barack Obama begins with an emphasis on removing noncombat forces rather than the infantry and others still trying to cement recent gains against a resilient Taliban.

“If it were up to me, I would leave the shooters for last,” he said.

The final decision is Obama’s. The commander in chief soon will receive from Gen. David Petraeus, the top U.S. and NATO commander in Afghanistan, a range of options on how to begin the withdrawal in July and how to pace it over perhaps 18 to 24 months, Gates said at this dusty logistics base in Kandahar province.

Obama planned to gather his national security team today for his monthly meeting on Afghanistan and Pakistan.

Military commanders typically want to keep as much firepower at their disposal as they can, for as long as they can, to achieve their mission. In the case of Afghanistan, the White House wants to ensure that the president’s oft-repeated promise to begin a withdrawal in July yields more than a token gesture. The war has grown increasingly unpopular in Congress.

Gates met with Petraeus shortly after he arrived in Kabul on Saturday. Both men will soon end their tenures. Gates retires June 30. Petraeus has been nominated to be the next CIA director, replacing Leon Panetta, whom Obama has chosen to succeed Gates at the Pentagon.

Gates said the main purpose of his visit was to deliver his personal thanks to troops. At each encounter Sunday, as he mentioned his gratitude for their efforts and the sacrifices of their families, he choked up.

“You all will be in my thoughts and prayers every day for the rest of my life,” he said in a shaky voice to a group of several hundred soldiers and Marines at Camp Dwyer, an outpost on a bleak patch of Helmand province.

Gates said Obama’s Cabinet has yet to begin a formal discussion of how to proceed with the planned troop withdrawal.

It has not even been decided, he said, whether Obama will announce only the number of troops to go home in July or whether he also will set a departure timeline, over a longer period, for all 30,000 of the extra troops that he sent to Afghanistan in 2010.