WELLINGTON (REUTERS) - The foreign minister of Tuvalu pulled out of the United Nations Ocean Conference opening in Portugal on Monday (June 27) after China blocked the participation of three Taiwanese included in the tiny Pacific island nation's delegation list, according to Radio New Zealand.

Taiwan, which China claims as its own territory, is not a member of the United Nations and its citizens are unable to attend UN events as representatives of Taiwan.

Tuvalu Foreign Minister Simon Kofe withdrew from the conference after China challenged the accreditation of three Taiwanese delegates included in Tuvalu's delegation, Radio New Zealand reported on Monday (June 27).

The nation of 12,000 people has had diplomatic ties with Taiwan since 1979, and is one of just 14 states around the world that continue to have diplomatic relations with Taiwan rather than China.

Taiwan is largely excluded from international organisations that have China as a member.

Asked for comment, Chinese foreign ministry spokesman Zhao Lijian reiterated Beijing's stance that Taiwan is part of China.

"The Taiwan authorities' attempts to squeeze into the United Nations Conference on the Oceans and the Law of the Sea by engaging in petty manoeuvres in the international arena or acting as followers of other countries will only demean themselves," he told a daily media briefing in Beijing.

Mr Kofe grabbed global attention for his nation last year when he addressed a global climate conference standing ankle deep in the sea to illustrate Tuvalu was "sinking".

Forty per cent of the capital district is underwater at high tide, and the country is forecast to be submerged by the end of the century.

Around 7,000 people, from heads of state to environmental activists, are expected to attend the conference that starts Monday.