The US has defended a proposed arms deal with Pakistan worth nearly a billion dollar to sell attack helicopters and missiles, saying the weapons would be used for internal counter-terrorism operations.

"This proposed sale of helicopters and weapons systems will provide Pakistan with military capabilities in support of its counter-terrorism operations inside the country," State Department Deputy Spokesperson Marie Harf  said.

"They are for internal counter-terrorism uses inside Pakistan -- so to be very clear about that, going after terrorists inside their own country," she said.

The USD 952 million deal approved by the State Department involves the US supplying Pakistan with 15 AH-1Z attack helicopters, 1,000 Hellfire missiles, engines, targeting and positioning systems and other equipment.