By Adrian Croft and Sabine Siebold
BRUSSELS (Reuters) - Germany called for closer military integration between groups of NATO countries on Tuesday as the alliance grappled with how to keep its defenses strong at a time of falling military spending.
Germany's proposal, discussed by NATO defense ministers at a Brussels meeting, is that big NATO nations act as "framework nations" leading a cluster of smaller NATO allies.
These clusters of countries would jointly provide some military capabilities or develop new ones for the benefit of the whole alliance, with the lead nation coordinating their efforts.
The idea could be a way of plugging gaps in the armory of European NATO countries such as air-to-air refueling aircraft, a shortage of which was exposed during the NATO bombing campaign of Libya in 2011.
The idea was welcomed by NATO Secretary-General Anders Fogh Rasmussen and by Britain but diplomats said some other countries, including France, had concerns about the proposal, fearing it could undermine countries' sovereignty and lead to over-specialization.
"Does that lead to a kind of specialization which could be dangerous if some nations specialize only in certain types of mission and disengage from other missions?," one diplomat said.
Some diplomats also worry that a cluster system could make it more difficult for NATO to use forces on operations because a parliament in one country could effectively veto military action by other nations in the cluster.
Germany, Italy, Spain and others declined calls by NATO in 2006 to move troops based in calm areas of Afghanistan to the violent south.
The United States has repeatedly voiced alarm about the growing gulf between U.S. military spending and capabilities and those of its European allies.
The German proposal would help share the cost of expensive military systems at a time when many NATO allies are slashing defense spending in response to the economic crisis.
Only four of the 28 NATO members - the United States, Britain, Greece and Estonia - met the alliance's target of spending 2 percent of their economic output on defense in 2012.
Groups of NATO allies already cooperate on some projects but the German idea would take that further by intensifying cooperation among a group of countries on a range of military projects.
NATO's Rasmussen said the German proposal was an example of how allies could "cooperate more closely with a view to acquiring and developing much-needed military capabilities".
British Defence Secretary Philip Hammond said London supported the German proposal. "We think this is a good initiative which has the potential to sidestep some of the delays that we have had in NATO processes in the past," Hammond told reporters in Brussels.
(Editing by Tom Pfeiffer)