Three years ago New Zealand agreed to take in 75 individuals a year from the low-lying atoll country of 11,000 people, which claims it is suffering from rising sea levels caused by global warming.

But Tuvalu Prime Minister Saufatu Sopo'aga said that fewer than 30 percent of the Tuvalu places in New Zealand quota, called the Pacific Access Category (PAC), had been filled.

"I am very frustrated by it," he told AFP.

He said he had raised the issue last month with New Zealand Prime Minister Helen Clark but got no satisfactory answer.

"It is not very transparent, they dont tell island governments what they are doing," Sopo'aga said.

In February, freak spring or "king" tides swamped Tuvalu's 26 square kilometres (10 square miles), producing frightening springs of seawater and flooding homes and part of the airport.

Sopo'aga said the emigrants were not yet being treated as so-called "environmental refugees" from the rising sea, but added that they "perhaps in the long term could be considered that way."

New Zealand Immigration Minister Paul Swain told AFP Thursday "there is a problem here and we are moving to review the scheme."

Swain said there would always be "huge tension" in such immigration schemes, where countries like New Zealand wanted the best migrants while poorer countries like Tuvalu would not want to give up their best people.

He said the rules were quite tough, "and so they should be", but accepted that as a result the quotas which apply to a number of Pacific countries were now no longer being filled.

Tuvalu's nine atolls, none of which rises more than 4.5 metres (15 feet) above sea level, lie 3,400 kilometres (2,100 miles) northeast of Australia.

SPACE.WIRE