The country joins the comprehensive and advanced agreement of the Trans-Pacific Partnership

WELLINGTON, New Zealand — The United Kingdom formally joined an Asia-Pacific trade group that includes Canada, Japan and nine other countries on Sunday at a meeting in New Zealand.

The trade bloc covers more than 500 million people and 15% of the global economy. For the UK, it is the most important trade agreement struck since leaving the European Union more than three years ago.

The UK first announced in March that it had reached an agreement to join the bloc, which was set up in 2018, after more than two years of negotiations. It is the first new member to join the bloc, called the Comprehensive and Progressive Agreement for the Trans-Pacific Partnership (CPTPP).

It also includes New Zealand, Australia, Brunei, Chile, Malaysia, Mexico, Peru, Singapore and Vietnam.

“We are honored to become the first new member of the CPTPP and to join this amazing community which now includes 12 economies spanning Asia Pacific and now Europe,” said UK Trade Secretary Kimmy Badnoch.

“This is a recent and ambitious deal and our joining this exciting, growing and forward-looking bloc is evidence that the UK’s doors are open for business,” he added.

Badinush said more than half a million Britons already work for companies in the bloc’s member states.

Shigeyuki Goto, Japan’s economic minister, said the UK would strengthen the bloc.

“The fact that this was done in a way that maintains the high standards of the agreement sets an exemplary precedent for future accession,” Goto said.

The deal comes as the UK seeks to become more involved in the Indo-Pacific region. Critics say the deal pales in comparison to the UK’s trade with its neighbors in the 27-nation European Union.

New Zealand Prime Minister Chris Hepkins said the UK’s addition to the bloc was good news for the region.

“Trade is not only a priority for this government, but it is essential to our economic recovery and to improving the lives and livelihoods of all New Zealanders,” said Mr. Hipkins.

Since leaving the European Union, the UK has also signed separate trade agreements with Australia and New Zealand.

The United States is not part of the bloc, after former President Donald Trump withdrew from his predecessor, the Trans-Pacific Partnership. China has applied to join the bloc.