EU and Southeast Asian nations will hold their first full summit in December, a sign that the two blocs are looking for closer ties amid concerns over security threats from China and Russia, officials told Reuters.

The summit, to be held in Brussels on Dec. 14 but yet to be publicly announced, is seen as a sign of "increasingly close relations in the current geopolitical context", one EU official said.

The move follows a U.S. "pivot" to Asia launched by the Obama presidency, amid increased attention on a region which sits on major trade routes and is rich in natural resources.

Previous meetings between the 27-nation EU and the 10-country Association of Southeast Asian Nations (ASEAN) have usually been attended by leaders holding the temporary presidency of the blocs.

The European Union is seeking to boost its clout in the region amid growing concerns there about China and the impact of Beijing's tensions with Washington, a second EU official said.

"When it comes to hedging against the U.S.-China rivalry, the EU is always the very top answer in the region," said the official, who is directly involved in talks with ASEAN nations.

A third EU official confirmed security issues would be a key part of the discussions as Brussels seeks a clearer stance from Southeast Asian nations on Russia's invasion of Ukraine.

China also claims almost the entire South China Sea, putting it at odds with some Southeast Asian neighbours which have their own claims.

The ASEAN secretariat did not reply to a request for comment. The governments of Indonesia, Vietnam, Singapore and Malaysia had no immediate comment. The Philippines' foreign affairs ministry said EU-ASEAN relations have been strong for decades.

Some EU countries, mostly in eastern Europe, want assurances from ASEAN partners that they would not help Moscow bypass Western sanctions and clear references to Russian "aggression" in Ukraine in a summit joint statement, diplomats said.

It is unclear whether they will succeed on this. Laos and Vietnam abstained in the U.N. vote on the Ukrainian war.

Myanmar's leaders would not be invited to the summit, reflecting the EU's criticism of the junta which took power by force after elections there in 2020. The country would be represented by an ambassador, multiple sources said, in line with other international gatherings after the military coup.

(Writing by Francesco Guarascio @fraguarascio; additional reporting by Karen Lema in Manila, Kate Lamb in Jakarta, Rozanna Latiff in Kuala Lumpur, Chen Lin in Singapore and Khanh Vu in Hanoi; editing by Nick Macfie)