US President Donald Trump signed into law the $717 billion annual defence policy bill, the earliest in the year the bill has become law in more than four decades.

“The National Defense Authorization Act (NDAA) is the most significant investment in our military and our warfighters in modern history, and I am very proud to be a big, big part of it,” Trump said before signing the bill on Monday.

“It was not very hard. You know, I went to Congress, I said let’s do it, we got to do it. We’re going to strengthen our military like never, ever before, and that’s what we did,” he said.

Trump signed the bill during a visit to Fort Drum, New York, where he was joined by Vice President Mike Pence, Deputy Defence Secretary Patrick Shanahan and the Joint Chiefs of Staff Joseph Dunford, reports The Hill.

This year’s NDAA authorizes about $639 billion for the base budget of the Pentagon and defence programmes of the Energy Department.

It also allows for another $69 billion for a war fund known as the Overseas Contingency Operations (OCO) account.

It fulfils several of the administration’s priorities to bulk up the military, including adding 15,600 troops across the Army, Navy, Air Force and Marine Corps.

The bill also follows the administration’s request for 77 F-35 fighter jets and goes beyond the its request for Navy ships, authorizing a total of 13 new vessels.

“We will replace aging tanks, aging planes and ships with the most advanced and lethal technology ever developed, and hopefully we’ll be so strong we’ll never have to use them,” Trump said.

The bill also gives troops a 2.6 per cent pay raise, the highest in nine years, The Hill reported.

On Monday, Trump made no mention of the bill’s namesake.

With the NDAA signed into law, Congress now turns its attention to passing a defence spending bill to make the dollar amounts authorized by the NDAA a reality.

The House passed a Pentagon spending bill in June, while the Senate is expected to start considering its version as soon as this week.