Samoa's appeals court on Friday rejected a last-minute bid to prevent the opposition from taking power, paving the way for the Pacific nation's first change of government in almost 40 years.

The ruling means parliament can sit on Monday, when the opposition FAST Party's leader Fiame Naomi Mata'afa is expected to be installed as Samoa's first female prime minister.

"In God's name, let change begin! Time to get to work for our people!" FAST posted on Facebook after the decision.

It was the latest twist in a six-week standoff following the April 9 general election, which has resulted in numerous legal challenges and appeals.

Should the results stand, Mata'afa's party will hold 26 seats in the 51-seat parliament, one more than the incumbent Human Rights Protection Party (HRPP).

Prime Minister Tuilaepa Sailele Malielegaoi, who has held the top job for 22 years, appears to be out of legal avenues to challenge the result.

Bu the veteran campaigner has found loopholes previously and further surprises cannot be ruled out.

When it initially appeared FAST was edging ahead, he evened the ledger by having an extra MP assigned to his party under provisions setting out the minimum quota of women in parliament.

He then persuaded head of state Tuimalealiifano Vaaletoa Sualauvi to call a second election for May 21.

Should the results stand, Fiame Naomi Mata'afa is expected to be installed as Samoa's first female prime minister
Should the results stand, Fiame Naomi Mata'afa is expected to be installed as Samoa's first female prime minister Fa’atuatua I le Atua Samoa ua Tasi (FAST) / Handout

The courts overturned both measures this week and a panel of appeal judges on Friday declined HRPP's bid for a stay on the rulings.

It leaves the nation of 220,000 on the brink of a seismic political shift unthinkable when FAST formed in July last year.

Samoa gained independence in 1962 after nearly 50 years as a New Zealand protectorate and the HRPP has been in power since 1982, apart from a brief coalition period in 1986-87.

FAST leader Mata'afa is the daughter of the independent nation's first prime minister and is seen as a pioneering feminist in the conservative, staunchly religious nation.

She was previously with the HRPP and served as Malielegaoi's deputy until they fell out last year over a suite of controversial laws introduced by the government to control the judiciary.

She said this week that the HRPP had begun to abuse its power after so long in office and it was time to make Samoa a functioning democracy again.

"I think what people are saying is we haven't had a participatory government for a long time and they would like to be more engaged in the process of governance," she told TVNZ.

She has previously been critical of Beijing's policies in the region and has called into question a major Chinese port project in the island nation.

China's foreign ministry on Thursday defended the project, saying it was would "promote the development of the local economy and create jobs".