U.S. presidential candidate Donald Trump on Wednesday called on Japan to drastically increase its financial contribution to maintain the American military facilities it hosts under a 1960 security treaty.

"Of course they should pick up all the expense. Why are we paying for this?" Trump, the front-runner in the Republican Party nomination race, said in an interview with CNN, referring to Japan, South Korea and other countries where the United States plays a role in defense.

Japan earmarked ¥189.9 billion ($1.7 billion) to host U.S. military bases in Japan in fiscal 2015 through March 31 as part of the costs necessary to station nearly 50,000 U.S. personnel here.