Defense Secretary Robert Gates said Sunday that the date for withdrawal of the full 30,000-troop surge in Afghanistan is even more important than the number of troops who leave next month.

During his farewell tour of military bases in Afghanistan, Gates said it’s “really not so much about where you start” that matters but the pace of the withdrawal over the next two years and when the surge troops will be leaving Afghanistan.

“What’s the bookend? Where are we headed? What’s the ramp look like?” Gates told reporters at Camp Dwyer in Helmand province. “I think that will be part of the discussion.”

Gates’ visit comes as President Obama begins to consider how many of the 100,000 U.S. troops here to begin withdrawing next month. Gates was an advocate of the 30,000-soldier increase that Obama ordered in late 2009.

The departure of U.S. military forces has potentially profound consequences both for its NATO allies and the insurgents troops are fighting. Gates, who is retiring at the end of the month, said he will discuss the issue when he returns to Washington and that Gen. David Petraeus will soon make recommendations on the start of the withdrawal.

Gates said he wanted to preserve combat power as much as possible. “If it were up to me, I’d leave the shooters until last,” he said, referring to combat forces. But he acknowledged that there were only so many support units, such as those involved in logistics and construction, and that the departing troops would likely be a combination of combat and support troops. “I think it will be a mix,” he said.

On Saturday, Gates predicted the number of troops leaving in July would be “modest,” and has stressed that the United States does not want to send a signal of wavering resolve to friends or enemies.

“I have every confidence that the decision that’s made will be a responsible one,” he said. “Nobody wants to give up the gains that have been won at such hard cost. And nobody wants to give our allies the excuse to run for the exits.”

Gates left Kabul Sunday morning and flew to military bases in Kandahar and Helmand provinces, the center of the U.S. military fight against the Taliban. In a voice full of emotion, he took the opportunity to thank U.S. soldiers and Marines for their sacrifices.

“More than anybody except the President, I’m responsible for you being here,” he told soldiers at Forward Operating Base Dalton in Kandahar. “I just want you to know I think about you every day. I feel your hardship and your sacrifice and your burden and that of your families, more than you can possibly know. You are, I believe, the best our country has to offer, and you’ll be in my thoughts and prayers every day for the rest of my life.”