ROME (Reuters) - Italy will send about 140 troops to join a NATO mission in Latvia set up to boost defenses against a possible Russian attack, Foreign Minister Paolo Gentiloni said on Friday.

The Western defense alliance agreed in July to deploy military forces in the Baltic states and eastern Poland for the first time and increase air and sea patrols, to reassure its allies after Russia seized Crimea from neighboring Ukraine. [L8N19U0PP]

During a visit to Rome by NATO Secretary-General Jens Stoltenberg, Gentiloni said Italy would send the troops to join a Canadian-led force in Latvia. They will probably be deployed in the spring of 2017, a foreign ministry official said.

The decision "is not part of a policy of aggression towards Russia, but one of reassurance and defense of our borders as an Atlantic alliance," Gentiloni added.

Italy will lead an ultra-rapid action task force in the former Soviet republic, a "spearhead" which will be equipped to intervene within five days in an emergency, Stoltenberg told Italian newspaper La Stampa.

Under the July accord, NATO pledged to move four battalions totaling 3,000 to 4,000 troops into northeastern Europe on a rotating basis. Germany and Latvia tested air defenses as part of the alliance's "Persistent Presence" exercise in September.

"This is not the Cold War, but we do not have the partnership we have been working on for years," Stoltenberg told La Stampa.

"We are in uncharted territory, we have never seen relations with Moscow like this before." he said.

(Reporting by Antonella Cinelli and Isla Binnie; Editing by Tom Heneghan)