US to Offer Cyberwar Capabilities to NATO Allies

File photo of the Pentagon, as seen from Air Force One, taken on Feb. 12, 2009. The Pentagon says the U.S. is offering to put its cyber-warfare capabilities to use on behalf of its NATO allies. Officials planned to announce it in the coming days as U.S. Defense Secretary Jim Mattis attends a meeting of NATO defense ministers in Brussels on Oct. 3-4. AP Photo/Charles Dharapak, File

BRUSSELS—Acting to counter Russia’s aggressive use of cyberattacks across Europe and around the world, the U.S. is expected to announce that, if asked, it will use its formidable cyberwarfare capabilities on NATO’s behalf, according to a senior U.S. official.

The announcement is expected in the coming days as U.S. Defense Secretary Jim Mattis attends a meeting of NATO defense ministers on Oct. 3-4.