Prime Minister Shinzo Abe spoke with U.S. President Donald Trump by phone for about 30 minutes May 1, but details of the conversation are officially shrouded in mystery.

The Cabinet Office has not divulged details of the discussion, but multiple sources close to the government who spoke to The Asahi Shimbun said it centered on Abe's summit talks with Russian President Vladimir Putin in Moscow on April 27 and future steps the two allies would take in response to North Korea’s failed missile launch on April 29.

It is no secret that Abe and Trump also spoke by phone before the Japanese leader left for Russia, but the government apparently decided not to release details this time around out of consideration for the sensitivity of the issues involved.