The success of a key NATO summit next week is hanging in the balance. Spain has announced that it cannot raise the billions of dollars needed to meet a new defense investment pledge.

Spain has asked to opt out of NATO's plan to increase members' defence spending to 5% of their gross domestic product, a move that could derail a summit at which the military alliance plans to ask them to commit to the target.

MADRID (Reuters) -Spanish Defence Minister Margarita Robles said on Friday her country is totally committed to NATO, a day after Madrid asked the alliance to be exempted from the proposed increase in the defence spending target to 5% of gross domestic product.