WASHINGTON (Reuters) - The U.S. government has approved Britain's request to have 50 of its older model Apache helicopters refurbished and upgraded by Boeing Co (>> Boeing Co) and other U.S. companies, a deal valued at around $3 billion (1.95 billion pounds), the Defence Department announced on Thursday.

The Pentagon's Defence Security Cooperation Agency (DSCA), which oversees foreign arms sales, notified U.S. lawmakers on Wednesday about the possible sale, which would include 110 T-700-GE-701D engines built by General Electric Co (>> General Electric Company), and a variety of acquisition sights, sensors and radar equipment.

Lawmakers have 15 days to block the sale, although such action is rare since deals are usually carefully vetted before any formal notification.

DSCA said the proposed upgrades and refurbishment of the 50 helicopters would allow Britain to work more closely and seamlessly with U.S. forces.

It said Britain would use the Apache helicopters to conduct various missions, including counter-terrorism and counter-piracy operations.

Lockheed Martin Corp (>> Lockheed Martin Corporation) is another key supplier on the programme, the government said.

(Reporting by Andrea Shalal; Editing by Andrew Hay)