China has invited North Korean leader Kim Jong Un to attend events in Beijing in September to commemorate the 70th anniversary of the end of World War II, according to a person familiar with the matter, according to the Wall Street Journal.

It wasn’t clear whether Kim would hold talks with Chinese President Xi Jinping if he travels to Beijing, but a visit by the North Korean leader would suggest that relations between the countries are stable. Kim has yet to meet another national leader or travel abroad since taking power at the end of 2011.

China is North Korea’s only major ally and traditional provider of diplomatic and economic support. However, Chinese officials say that in recent years Beijing has become increasingly frustrated with Pyongyang’s belligerent behavior, including frequent missile tests and pledges to build up its nuclear arsenal.

“There is no reply yet” to the invitation, said the person familiar with the issue, adding that despite strained Beijing-Pyongyang ties China strongly favors dialogue with North Korea.

The press office of the Communist Party’s International Liaison Department, the office which often handles the Chinese leadership’s contacts with North Korea, said it wasn't aware of any invitation.

China’s foreign ministry said invitations have been issued to leaders of some Asian and other countries but declined to specify which ones.