By David Alexander
WASHINGTON (Reuters) - Defense Secretary Leon Panetta faces an unexpectedly challenging NATO meeting this week that could expose embarrassing rifts in the Western alliance just as President Barack Obama prepares to host a summit of allied leaders this spring in the middle of an election year.
The NATO meeting in Brussels on Thursday and Friday comes a week after Panetta previewed a defense budget that calls for slashing American force numbers in Europe, part of a new U.S. military strategy that puts Asia and the Middle East as top priorities with Europe a lowly third.
The meeting of alliance defense ministers also follows an announcement by President Nicolas Sarkozy that French troops will withdraw from Afghanistan in 2013, a year ahead of the agreed 2014 timeline. Sarkozy urged the rest of NATO to withdraw as well, threatening to upend the allies' well-settled strategy.
Panetta's budget plans, which call for the removal of two heavy infantry brigades from Europe, have raised concerns about U.S. commitments to European security and whether the United States will have the forces to fulfill its treaty obligation for the region's collective defense.
The U.S. Army has four combat brigade teams in Europe, so removing two would cut the force in half. A combat brigade team has about 3,500 to 5,000 soldiers.
Ian Brzezinski, a senior fellow at the Atlantic Council think tank in Washington, said the European allies would be looking for Panetta to explain what the new U.S. force posture means for the trans-Atlantic alliance.
"That had better be the first top-line objective for the administration because that gets to the essence of the trans-Atlantic bargain and the solidarity of NATO," said Brzezinski, who was deputy assistant secretary of defense for Europe and NATO Policy during President George W. Bush's administration.
"What are the withdrawal of these forces - two BCTs (brigade combat teams) and this air wing - going to mean about America's commitment to NATO and Article 5," which requires members of the alliance to come to each others' defense, he said.
Brzezinski noted that heads of the U.S. European Command, including the commander, Admiral James Stavridis, have told Congress the U.S. military might not be able to fulfill its treaty obligations with fewer than four Army combat brigades.
Stavridis told the armed services committees of Congress in 2010 that maintaining four brigades was "critical" to the U.S. mission.
"Without the four brigade combat teams and one tactical intermediate headquarters capability, European Command assumes risk in its capability to conduct steady-state cooperation, shaping and contingency missions," Stavridis said in his testimony. "Deterrence and reassurance are at increased risk."
The Pentagon budget request, which seeks to trim $487 billion in spending over the next decade, raised concerns on an array of other issues for Europe, analysts said.
With the U.S. Army combat presence in Europe reduced by half, would there be enough joint practice time to ensure NATO forces can work together in military operations like the recent Libya campaign?
Will the U.S. decision to delay purchases of the F-35 Joint Strike Fighter drive up the cost of individual planes for partner nations in the project, many of them NATO allies?
The impact of the U.S. decision on the cost of the F-35 is unclear, but Brzezinski noted that when programs get pushed back, generally "you end up paying more, not less."
To address the training issue, the Pentagon has pledged to regularly rotate brigades into Europe, a move it says will give European forces even greater exposure to different American units and improve their ability to work together. But analysts are skeptical.
"The new defense strategy talks a lot about working with partners but we're talking about battlefield operations ... that are incredibly technologically complex," Brzezinski said.
"I'm not convinced that a BCT (brigade combat team) based in Texas is going to be as effective in promoting the interoperability, jointness and preparedness to operate globally than one based in Germany or Italy," he said. "I think the administration's got a lot of explaining to do about how rotational deployments are actually going to be more effective."
Beyond reassuring NATO allies over the implications of the U.S. defense budget, Panetta will have to work to avert any appearance of a rush for the exits in Afghanistan after Sarkozy, facing his own re-election challenges, announced the early French withdrawal from Afghanistan at a news conference with Afghan President Hamid Karzai last week.
"For Sarkozy to do this by himself in front of the media ... surprising even his own government was just shocking and it's going to have an impact beyond Washington," said Barry Pavel, director of the international security program at the Atlantic Council.
Pavel said he expected U.S. and NATO leaders to try to avoid having a series of countries drop out of the coalition in Afghanistan over the next few weeks.
"If it's France and then country 'y' and then country 'z' over the next three to four weeks, that's going to look really bad," Pavel said. "And it raises questions about the U.S. commitment in the midst of everybody else getting out."
"So I would imagine the White House would put on a pretty firm push to ... put a security fence around this and firm up the rest of the coalition. Otherwise they're hanging on by a thread and that looks bad in an election year."
The unexpected discord within NATO comes at an awkward time for the Obama administration. The president is due to host a summit of NATO leaders in Chicago in May, a meeting that had been expected to showcase Atlantic alliance unity before the U.S. presidential election in November.
(Reporting By David Alexander; editing by Christopher Wilson)