U.S. Defense Secretary Robert Gates made an unannounced trip to Belgium Sunday for a secret meeting with his top commanders on the situation in Afghanistan.

Pentagon Press Secretary Geoff Morrell would not provide many details of the highly unusual gathering, except to say Gates wanted to hear an interim report from the top U.S. and NATO commander in Afghanistan, General Stanley McChrystal, on his assessment of the situation in the country and the resources he has to deal with it.

"He [Gates] wanted an opportunity to speak first hand with his commanders and his senior military advisers about how the assessment was unfolding so that he could gain as clear an understanding of the situation as possible," he said.

Members of the general's civilian advisory board indicated last week that they have told him he needs more troops, something Gates has said in the past he would be reluctant to approve.  Gates and President Barack Obama have already ordered a near doubling of the U.S. troop presence in Afghanistan to 68,000 by the end of the year.  McChrystal is to provide Gates with a formal assessment in about two weeks, but Morrell says the general's assessment is not yet completed.

"This meeting speaks to the fact that this is still a work in progress, and that the secretary wanted to get a sense of where it was headed so that he can begin to inform his thinking and prepare for the likely assessment that will be made in the coming weeks," he said

Morrell says there was no particular development that prompted the meeting, but he noted that July had the highest number of American troop deaths in Afghanistan since the U.S.-led invasion eight years ago, and that August is already on pace to be a particularly bad month, as well.

"The situation on the ground there is such that the secretary wants to make sure that he and his commanders are on top of it, and wants to get a sense of where they are heading right now with this assessment," said Morrell.

The meeting Sunday at the U.S. air base in the Belgian town of Chievres, near NATO's military headquarters, also included General McChrystal's deputy, Lieutenant General David Rodriguez, the supreme NATO commander, U.S. Admiral James Stavridis, and the commander of all American forces in the Middle East and South Asia, General David Petraeus.  The top U.S. military officer, Joint Chiefs Chairman Admiral Mike Mullen also attended, as did the Pentagon's top policy official, Under Secretary Michele Flournoy.

Morrell says the meeting lasted several hours and provided the secretary an opportunity he does not get in regular video conferences with the commanders.

"There's nothing that can compare to sitting down face to face, with time not being a real issue, and for them to take several hours to sit down and discuss these things at length in a very candid and personal way and dive into them more deeply than he could via a secure video teleconference," he said.

Secretary Gates and other top U.S. defense officials have said it is crucial to do everything possible to at least begin to get control of security in Afghanistan during the next year or so.  That is why Gates curtailed the tour of the previous U.S. and NATO commander in Afghanistan, General David McKiernan, and put General McChrystal in place to implement a new strategy, focusing on protecting Afghan civilians and reducing what has been the growing Taliban influence in many areas.