NUSA DUA, Indonesia - Prime Minister Stephen Harper has used the platform of one international leaders' summit to fire a torpedo into the hull of another.

Harper stepped to the sidelines of the Asia-Pacific Economic Cooperation gathering on this idyllic Indonesian tourist island Monday to formally confirm he'll boycott next month's Commonwealth summit in Sri Lanka.

Perhaps more significantly, Harper threatened that Canada could cut the purse strings to the 64-year-old Commonwealth organization due to ongoing human rights abuses by the host Sri Lankan government.

The prime minister cited everything from the impeachment of a chief justice to allegations of extra judicial killings and disappearances and the jailing of political opponents and journalists.

"In the past two years we have not only seen no improvement in these areas, in almost all of these areas we've seen a considerable rolling back, a considerable worsening of the situation," Harper said in a brief availability at the APEC summit site.

"Based on that, I have made a decision I will not attend the Commonwealth leaders' summit this fall."

Harper said he made the move with "somewhat of a heavy heart," but he has been threatening the boycott since the last Commonwealth leaders' meeting in Australia in 2011, so it comes as little surprise.

But his frank displeasure with entire organization, and sabre rattling over funding, raises the stakes.

Canada contributes about $20 million annually to various Commonwealth initiatives, including $5 million to the secretariat that runs the organization, making Canada the second largest financial contributor.

The grouping of 54 countries formerly under British rule is facing an existential crisis in a global community crowded with international clubs — including those like the Pacific Rim leaders' summit here that are explicitly focused on trade and commerce.

Canada could skip a year at APEC — U.S. President Barack Obama was forced by Washington's budget crisis to miss the Bali summit and sent Secretary of State John Kerry in his stead — with barely a notice.

But any extended Canadian absence or cash withdrawal from the Commonwealth could be fatal to the tottering enterprise. Sri Lanka holds the chair for the next two years.

"Obviously we will examine our engagement and our financing of the Commonwealth, which is quite considerable, to make sure that we are wisely using taxpayer dollars and reflecting Canadian values," Harper said.

"But this is a decision the Commonwealth has made and the Commonwealth will have to live with it."

Paul Dewar, the NDP foreign affairs critic, said while his party supports the idea of a Commonwealth boycott, it's not in favour of linking funding to the move.

"It's a false and disingenuous connection between the merits of an individual member state and those of the broader institution," Dewar said in an email.

"If they wanted to send a stronger message they could have moved to remove Sri Lanka from the Commonwealth until there are concrete improvements on human rights."

Harper held bilateral meetings Monday on the sidelines of the APEC summit with the prime ministers of Australia and New Zealand, two other significant Commonwealth players.

Harper's office said the Commonwealth decision was not discussed — however New Zealand Prime Minister John Key later told reporters he did in fact raise the matter with Harper.

"Definitely, yes, I'm going," Key said of Sri Lanka.

Australia's Tony Abbott also told reporters he will attend.

"You do not make new friends by rubbishing your old friends or abandoning your old friends," said the Australian.

While noting every country makes its own calls on such matters, Key said that "if we decided you were going to have to meet New Zealand standards to attend a meeting, there'd be lots of countries we wouldn't go to."

"I just don't know that's really going to help New Zealand."

Key even credited Chinese President Xi Jinping for selling the virtues of engaging all countries here at the APEC summit.

"It was one of the points the Chinese president actually made, I think it was yesterday or today, but basically engagement increases understanding and actually leads to change over time," said the New Zealand prime minister.

So Harper remains the only leader to boycott the Colombo conference, and won't even send a cabinet-level representative. Parliamentary secretary Deepak Obhrai will represent Canada at the mid-November summit.

It is not the first time the Harper government has taken its ball and gone home on the international front.

The prime minister snubbed China for four years after coming to office, citing human rights concerns, and Canada refused to participate in a United Nations disarmament conference because North Korea was the chair.

Last year, the government shuttered its embassy in Tehran to the dismay of many international observers, who argued a middle power like Canada can only exert influence through engagement.

The Sri Lankan government in Colombo repeatedly has accused Canada of playing domestic politics on its back.

Canada is the world's largest home of expatriate Tamils, the Sri Lankan minority from which sprung a civil war that lasted decades before ending in a bloody climax in 2009.

Canada's Tamils are a tightly knit community focused in the Greater Toronto Area, making them a small but politically potent constituency courted by both the federal Liberal and Conservative parties.

While few Canadians could probably cite a single initiative of the Commonwealth grouping or its purpose, those few who care are heavily vested.

"The feedback we've had from Canadians has been absolutely overwhelming," said Harper, "that they would not expect the prime minister of Canada to attend such an summit."

As for that other leaders' conference, Harper wraps up talks at the APEC summit on Tuesday before returning to Canada in mid-week.

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