Trump: Talks with DPRK have started

Zhang Liangui, a Korean studies expert at the Party School of the Central Committee of the Communist Party of China, said there are still many uncertainties in the dialogues between Trump and Kim.

Zhang said the US never changed its stance on the denuclearization of Korean Peninsula. If the DPRK continues to hold an ambiguous attitude on this issue, the possibility of finally using force to resolve the issue still exists.

He said Pyongyang still wants to talk, but it wants Washington to recognize it as a nuclear-armed country.

Heather Nauert, US State Department spokeswoman, said on Tuesday that the "big part" of the inter-Korean dialogue will be Trump's upcoming meeting with Kim, whenever that takes place.

Abe stressed to Trump "the importance of achieving the complete, verifiable, and irreversible denuclearization, as well as the abandonment of missile programs of North Korea", according to a White House news release.

"Tokyo is less certain about how the president views the summit with the North, and Abe's visit will therefore be critical," said Michael J. Green, a researcher at the Center for Strategic and International Studies.

According to Ruan Zongze, senior research fellow of the China Institute of International Studies, Abe's visit has an intention to fulfill Japan's "private goals".

Tokyo wants to use the chance to ask Washington to help solve its disputes with Pyongyang over the kidnapping of hostages, among other issues, which may cause the Korean Peninsula discussions to get out of focus, Ruan said.

Abe on Tuesday said he would "share understanding and recommendation" with Trump during his two-day visit.

Reuters contributed to this story.