Samoa's expected new prime minister has pledged to shelve a $US100 million ($NZ139m) Beijing-backed port development, calling the project excessive for the small Pacific island that is already heavily indebted to China.

Fiame Naomi Mataafa, the opposition leader set to become Samoa's first female prime minister after a weeks-long political impasse, said she intended to maintain good relations with China but she had more pressing needs to address.

The proposed construction of the wharf in Vaiusu Bay has been a divisive issue in Samoa, playing a part in April elections where long-serving leader Tuilaepa Sailele Malielegaoi lost his parliamentary majority.

The project has also threatened to spark a waterfront contest in the Pacific as the United States and its allies respond to China's growing regional influence.

Fiame, who is expected to become leader after Samoa's top court on Monday ruled against a challenge to the election result, told Reuters there were more pressing needs than building a new port.

"Samoa is a small country. Our seaports and our airports cater for our needs," Fiame said by phone from Samoa's capital, Apia.

"It's very difficult to imagine that we would need the scale that's being proposed under this particular project when there are more pressing projects that the government needs to give priority to."

Her stance marks a decisive break from Tuilaepa, whom Beijing has counted on as a close ally of China over his two decades as leader.

"The level of indebtedness of our government to the government of China was a pressing issue for voters," said Fiame, a former deputy prime minister who joined the opposition FAST party last year. Her government would maintain good relations with both China and the US, she added.

China is the single largest creditor in Samoa, a country of 200,000 people, accounting for about 40 percent, or some $US160m, of the small nation's external debts.

Tuilaepa has previously said Pacific countries only have themselves to blame if they fall into unsustainable debt.

He has frequently described the Vaiusu wharf in parliament as a "China-funded project" that would create much-needed jobs and increase trade and tourism. Port designs and funding arrangements have not been disclosed.

The project was in the final stages of negotiation with China, with work set to commence when international borders reopen, according to a January report in the Samoa Observer, citing Tuilaepa.

The Chinese foreign ministry and Tuilaepa's office did not respond to questions.

Fiame's government could be formed as early as Friday, although legal challenges may cause delays.