WASHINGTON » The National Security Agency is defending its tracking of foreign cellphones overseas. It says the practice is legal under a U.S. presidential order governing all U.S. government spying.

The agency said today it isn’t tracking every foreign phone and call, and that it takes measures to limit how much U.S. data is collected.

The Washington Post reported this week that the agency is gathering location data for up to 5 billion cellphones globally every day, including some American data, according to documents from former NSA contractor-turned-fugitive Edward Snowden.

Spokeswoman Vanee Vines says the practice is legal under a White House order that governs U.S. espionage, known as Executive Order 12333. She says NSA analysts must treat any U.S. citizens’ data they accidentally gather differently.