By Mike Stone

WASHINGTON (Reuters) - Sales of U.S. military equipment to foreign governments rose 33 percent to $55.6 billion in the fiscal year ended Sept. 30, a U.S. official told Reuters on Tuesday, as looser restrictions on sales have begun to increase arms deals.

The increase in foreign military sales came in part because the Trump administration rolled out a new "Buy American" plan in April that relaxed restrictions on sales while encouraging U.S. officials to take a bigger role in increasing business overseas for the U.S. weapons industry.

President Donald Trump wants to make the United States, already dominant in the global weapons trade, an even bigger arms merchant to the world, U.S. officials have said, despite concerns among human rights and arms control advocates.

There are two major ways foreign governments purchase arms from U.S. companies: direct commercial sales, negotiated between a government and a company; and foreign military sales, in which a foreign government typically contacts a Department of Defense official at the U.S. embassy in their capital. Both require approval by the U.S. government.

About $70 billion worth of foreign military sales notifications went to Congress this year, slightly less than the previous year, an administration official said.

The $55.6 billion figure represents signed letters of agreement for foreign military sales between the United States and allies.

The largest U.S. arms contractors include Boeing Co , Lockheed Martin Corp , Raytheon Co , General Dynamics Corp and Northrop Grumman Corp .

Numerous missile defense deals have gone through in the past year, including Poland and Romania's purchases of the Patriot missile defense system made by Lockheed and Raytheon.

(Reporting by Mike Stone in Washington; Editing by Steve Orlofsky and Dan Grebler)