WASHINGTON, Dec 19 (Reuters) - The Pentagon said on Monday it approved the sale to Australia of 10 C-27J transport aircraft built by L-3 Communications Holdings Inc and Finmeccanica SpA unit Alenia, as well as associated equipment, in a deal worth about $950 million. The Defense Security Cooperation Agency, which oversees major arms sales, said it notified Congress on Friday about the sale, which would also include 23 engines built by Britain's Rolls-Royce Group Plc and an array of sensors and radar systems. U.S. lawmakers have 30 days to block the sale, although such action is rare. The Pentagon agency said the proposed sale would allow the Australian Defense Force (ADF) to improve its capability to meet current and future air mobility needs and humanitarian operations and disaster relief efforts in Southeast Asia.