WASHINGTON-- U.S. President Donald Trump said Tuesday he is allowing South Korea and Japan to buy more U.S. military equipment but stopped short of providing any details.

The message on Twitter came as tensions have heightened following North Korea's sixth and most powerful nuclear test on Sunday. Pyongyang claimed it was a successful test of an H-bomb that can be mounted on a long-range missile.

"I am allowing Japan and South Korea to buy a substantially increased amount of highly sophisticated military equipment from the United States," Trump said.

The White House earlier quoted him as making similar remarks during two phone calls with South Korean President Moon Jae-in last week and earlier this week.

Trump provided his "conceptual approval for the purchase of many billions of dollars' worth of military weapons and equipment from the United States by South Korea," it said in a readout on Monday's phone call.

Asked about the remark, Moon's office said it probably referred to the leaders' "in-principle" agreement to hold discussions in the future about U.S. provision of advanced weapons or technologies required to strengthen South Korea's defense capabilities.

However, a South Korean presidential official, who spoke on condition of anonymity, said Trump made no such remark during the phone call.

Source: Yonhap News Agency