They were some of Harper's toughest words yet on the global impasse that played out at the G20 summit over the last two days in the imperial Russian capital, pitting Moscow against Washington.
"The Security Council and the United Nations are very important institutions, obviously we would prefer to see global consensus on this," Harper said at a closing news conference.
"But I think we share the view of our allies that when we see developments that we think in the long term are dangerous for the planet and therefore for us as well, we are simply not prepared to accept the idea that there is a Russian veto over all of our actions."
A joint statement was released just as leaders began to leave St. Petersburg, declaring the regime of Bashar Assad responsible for the strike against civilians last month in a Damascus neighbourhood.
"The world cannot wait for endless failed processes that can only lead to increased suffering in Syria and regional instability," says the statement.
"We support efforts undertaken by the United States and other countries to reinforce the prohibition on the use of chemical weapons."
The statement stopped short of explicitly calling for military action against Syria. But Canada, Australia, France, Turkey and Saudi Arabia have all said they do endorse a military strike.
At a dinner the evening before, leaders expressed their views about the prospect of a punitive strike against Syria for its alleged use of chemical weapons against its own people last month.
Russian President Vladimir Putin's position is that only the United Nations Security Council, on which Russia has a veto, should be allowed to order a strike against any nation. That stance has been echoed by several other countries, the European Council and the Vatican, even as they decry the use of chemical weapons.
At his own closing news conference on Friday, Putin repeated his assertion that he believes it was Syrian rebels — not the regime of Bashar Assad — that used chemical weapons in a Damascus suburb. Putin has said he would continue to support Assad's government militarily.
Harper cited the suffering of First World War veterans struggling from the after-effects of mustard gas at Sunnybrook Hospital in Toronto, the prime minister's home town.
"As I pointed out last night, even in the Second World War, even in the war against fascism and Hitler, those forces did not on the battlefield resort to chemical weapons," Harper said.
"I really do believe here that if we're going to sit back and allow a regime to try and win a military conflict through the use of chemical weapons, we are in new territory. We are in brand new territory that is extremely dangerous and that there would be no turning back from."
U.S. President Barack Obama, who has been under intense scrutiny during the summit, is also facing a tough battle at home to gain support for a military strike in Congress.
Harper defended his American counterpart, saying he and others do not "seek military adventure for its own sake."
"President Obama has worked hard to withdraw the United States from various past military operations. ... What President Obama and others are proposing is not something they're doing for popularity either."
In the absence of consensus, some nations announced they would be addressing the chemical attack in another way.
Harper also announced Friday the government would contribute $45 million in further help for Syria.
The money will go to organizations that provide food, clean water, sanitation, shelter and protection to civilians, as well as Syrians who have fled the country. Canada has contributed a total of $203.5 million since last January.
For the first time, the G20 summit included a meeting of foreign ministers — a sort of release valve for the pressure around the Syria crisis.
Items leaders agreed on included:
— a flexible approach to spurring economic growth and jobs, while keeping debts and deficit in check. This was radically different from the hard debt-to-GDP ratio targets that Harper was pushing for nations to adopt.
— a commitment to the automatic exchange of tax information among nations, rather than just on a by-request basis. The G20 nations also urged other countries to get on board.
— a directive to each country to look for ways to unlock investment dollars within the private sector, particularly for major infrastructure projects. The G20 had been examining the wealth held by mutual funds, insurance companies and other bodies.
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