WASHINGTON (REUTERS) - United States President Donald Trump said the United States needs more submarines but he wants to buy them at a lower cost, resuming his push to get defence contractors to cut the prices they charge the Pentagon.

"We're lacking submarines and we're going to build new submarines but the price is too high so I'm cutting the prices way down," Trump said in an interview on Fox News to be broadcast later on Thursday (Jan 26).

Two US-based companies, General Dynamics Corp's Electric Boat division and Huntington Ingalls Industries' Newport News Shipbuilding, build the Navy's nuclear-powered submarines.

Trump, who took office on Friday, made increasing military spending a key part of his campaign.

Since winning the November election, he has pressured US defence contractors to reduce the cost of the products they sell to the Pentagon.

In December, Trump received a pledge from the chief executive of Lockheed Martin to cut the cost of the F-35 fighter jet after Trump complained in a tweet about the plane's price tag and said he would ask Boeing to offer a cheaper alternative.