WASHINGTON (AFP) - US President Donald Trump told Japanese leader Shinzo Abe on Wednesday (April 5) that Washington will continue to build its military capabilities to defend against a North Korean attack, the White House said.

The leaders spoke by phone one day after Pyongyang fired a ballistic missile into the Sea of Japan, in what analysts said was a warning ahead of a US-China summit at which North Korea's accelerating atomic weapons program is set to top the agenda.

Trump "made clear that the United States will continue to strengthen its ability to deter and defend itself and its allies with the full range of its military capabilities," the White House said in a statement about the call.

"The President emphasised that the United States stands with its allies Japan and South Korea in the face of the serious threat that North Korea continues to pose."

Though the White House has previously made similar statements, the call came hours before Trump hosts Chinese President Xi Jinping for a two-day summit at his Mar-a-Lago estate in Florida.

Trump has said the United States is prepared to go it alone in bringing Pyongyang to heel if China - North Korea's top ally - does not step in.

In Tokyo, Abe said Trump had reaffirmed that all options are available in dealing with North Korea's nuclear and missile programs.

"I told (President Trump) that Japan is watching closely how China will cope with this North Korean issue," the prime minister told reporters after the 35-minute conversation.

"President Trump then made a strong remark, saying all options are on the table."

Abe was meeting Trump at the Mar-a-Lago estate in February when North Korea launched a rocket, setting off a controversy when the leaders set up an impromptu, alfresco "situation room" in full view of the resort's guests.