MANILA (Reuters) – A scheduled meeting between the foreign ministers of China and Vietnam was canceled on the sidelines of a regional gathering, Chinese embassy officials said, amid growing tension between the two countries over the South China Sea.

Vietnam had held out for language that noted concern about island-building and criticized militarization in South China Sea in the communique on Sunday from foreign ministers of the Association of South East Asian Nations (ASEAN).

Vietnam has emerged as the most vocal opponent of China’s claims in the waterway, where more than $3 trillion in cargo pass every year.

The Chinese embassy officials gave no reason for the cancellation of the meeting scheduled for Monday in Manila between China’s Wang Yi and Vietnam’s Pham Binh Minh.

A Chinese foreign ministry official said they had “already met”. Vietnam’s foreign ministry did not respond immediately to a request for comment.

State media in Vietnam said the ministers had held a “pull aside” meeting and exchanged views. It showed pictures of them shaking hands.

Although the language in the ASEAN communique reflected that in previous years, some countries pursuing deeper business ties with Beijing, such as Cambodia and the Philippines, had argued for dropping it.

Beijing is sensitive to even a veiled reference by ASEAN to its reclamation of seven reefs and its military installations in the South China Sea, which it claims in almost its entirety despite the competing claims of five other countries.

Tension has risen since June, when Vietnam infuriated China by drilling for oil and gas in an offshore block that Beijing disputes. The exploration was suspended after diplomatic protests from China.

After the ASEAN meeting, China’s foreign minister had called out “some countries” who voiced concern over island reclamation.

Wang said that China had not carried out reclamation for two years. “At this time, if you ask who is carrying out reclamation, it is definitely not China – perhaps it is the country that brings up the issue that is doing it,” he added.

Satellite images have shown that Vietnam has carried out reclamation work in two sites in the disputed seas in recent years.

On Tuesday, the state-run China Daily cited unnamed sources as saying Vietnam had tried to hype up the reclamation issue in the communique, pointing out that Vietnam has accelerated its land reclamation in the South China Sea.

“Undoubtedly, what Vietnam has done is the trick of a thief crying ‘stop thief,'” the paper quoted one of the sources as saying.

Australia, Japan and the United States on Monday urged Southeast Asia and China to ensure that a South China Sea code of conduct they have committed to draw up will be legally binding and said they strongly opposed “coercive unilateral actions”.

China has strongly opposed what it calls interference by countries outside the region in the South China Sea issue.

Meeting Japanese Foreign Minister Taro Kono on the sidelines of a regional security forum in Manila on Monday, Wang urged Japan to respect the efforts of China and ASEAN countries and play a more constructive role for regional peace and stability.

“Don’t always make trouble behind the backs of other countries and provoke quarrels,” the ministry cited Wang as saying.

(Reporting by Christian Shepherd; Additional reporting by Ben Blanchard in BEIJING; Editing by Michael Perry)