U.S. President Donald Trump has said talks with North Korea are off the table for now, the White House said Wednesday, after Pyongyang conducted it sixth and most powerful nuclear test.

Trump made the remark during a phone call with British Prime Minister Theresa May on Tuesday during which the leaders discussed Sunday's test of what North Korea claimed was an H-bomb that can be mounted on a long-range missile.

"President Trump reiterated that now is not the time to talk to North Korea, and made clear that all options remain open to defend the United States and its allies against North Korean aggression," the White House said in a statement.

The two leaders agreed to continue working closely together to apply diplomatic and economic pressure on North Korea, noting the latest "reckless act" only strengthens the world's determination to confront the growing threat from the regime.

Trump also held a phone call with Australian Prime Minister Malcolm Turnbull.

During the talks, the U.S. president "reaffirmed his commitment to defending the homeland, territories, and allies of the United States, using all available diplomatic and military capabilities," according to another White House statement.

Both sides condemned North Korea's belligerent actions and agreed to intensify efforts to denuclearize the country. (Yonhap)