Prime Minister Shinzo Abe headed for Ulan Bator on Thursday to attend a summit of Asian and European leaders where he is expected to call for an international ruling rejecting China's claims to historic rights over the South China Sea to be respected.

The Asia-Europe Meeting, or ASEM, is the first major international gathering since Tuesday's ruling by the Permanent Court of Arbitration in The Hague on the maritime case brought by the Philippines. China immediately rejected the ruling.

"I'll underscore the importance of the rule of law and peaceful resolution" of the issue, Abe told reporters at Tokyo's Haneda airport.

Whether a bilateral meeting will take place between Abe and Chinese Premier Li Keqiang on the sidelines of the two-day summit beginning Friday is an issue of intense speculation.

"I would like to exchange opinions" with Li as well as South Korean President Park Geun-hye, Abe said.

With tensions in the South China Sea in mind, the ASEM leaders may take this opportunity to collectively warn against any unilateral attempts to alter the status quo in territorial and other international disputes.

Abe is also expected to call for further cooperation on counterterrorism at the summit, which will be attended by top leaders or high-level representatives from more than 50 countries and organizations.

The leaders will likely condemn the July 1 terrorist attack in Dhaka, in which seven Japanese were among the 20 hostages killed.

Abe is scheduled to hold talks Thursday with Mongolian officials including President Tsakhiagiin Elbegdorj to discuss cooperation between the two countries.

He also plans bilateral meetings with the leaders of Germany, Bangladesh, Cambodia and the European Union, according to Japanese officials.

The summit will allow European and Asian leaders to discuss the implications of and their response to Britain's vote last month to leave the European Union.