"Yesterday NATO formally agreed to Greece's request for assistance for the Olympics," the Dutch secretary-general told reporters in advance of a NATO summit in Istanbul Monday and Tuesday.
"I'm pleased by this very concrete manifestation of NATO solidarity," he said.
"This assistance does not mean NATO is now in charge of security during the Olympics -- NATO is of course supporting the Greek efforts."
The decision, which was taken at a meeting of NATO ambassadors on Wednesday, was expected after Greece requested the alliance's help to safeguard the Olympics following the March 11 bombings in Madrid.
The plans involve AWACS surveillance plans, NATO's Mediterranean fleet and the alliance's batallion for biochemical warfare.
Greece itself is mounting its biggest-ever security operation for the August 13-29 Games, deploying 70,000 personnel at a cost of about one billion euros (1.2 billion dollars).
Safety concerns have been raised by a number of low-level bomb attacks in Athens in the run-up to the Olympics which the authorities have blamed on local fringe extremist groups.