BUFFALO, N.Y. -- When Army Sgt. Patrick Hart decided a decade ago that he would not serve in the war in Iraq, he expected to follow the same path as thousands of American war resisters during the Vietnam era and take refuge across the border.

But after five years of wrangling with the Canadian immigration system, he came back to the U.S. -- and ended up in a military prison.

The country that once welcomed war resisters has developed a much different reputation during the conflicts in Iraq and Afghanistan: Supporters say no U.S. soldier who has sought legal residence in Canada, either as a refugee or on humanitarian grounds, has been successful.

"Nobody's won," said Hart, a Buffalo native who exhausted his legal options then turned himself in to the Army, was court-martialed for desertion and sentenced to two years in prison.

There are an estimated two dozen U.S. military members still waiting out their fate in Canada, and the resisters' movement is seen as nearing a crossroads. With a national election three months away, supporters are hopeful for a Liberal Party victory and more sympathetic stance toward American military exiles, but bracing for the possibility Conservative Prime Minister Stephen Harper wins re-election.

Liberal Party leader Justin Trudeau has not committed to letting the resisters stay, but many are buoyed by his family history. It was his father, Pierre Trudeau, who while prime minister during the Vietnam War said Canada should be "a refuge from militarism."

"Why not do it again? It's only a couple of dozen people," said Michelle Robidoux, spokeswoman for the War Resisters Support Campaign in Toronto, which has been lobbying members of Parliament.

After a flurry early on, between 2004 and 2006, it's been at least four years since any known residency requests have been filed, Robidoux said.

Besides Hart, at least three other soldiers who were deported or left Canada have been sent to prison: Pfc. Kim Rivera, a mother of five, was sentenced in 2013 to 10 months; Spc. Clifford Cornell of Mountain Home, Arkansas, received a one-year term in 2009, and Pfc. Robin Long of Boise, Idaho, was sentenced in 2008 to 15 months.

Some deserters face court-martial but the majority are discharged on less-than-honourable terms. Army officials said more than 20,000 soldiers have deserted since 2006.

Canada's immigration laws have tightened since the Vietnam War, the support campaign said, giving U.S. soldiers few options other than to try for refugee status based on the fear of persecution if made to go home.

Government guidance issued to immigration officers in 2010 requires them to consult supervisors on U.S. military cases and spells out that desertion is a crime that may render those who've left the military as criminally inadmissible to Canada.

"Military deserters from the United States are not genuine refugees under the internationally accepted meaning of the term," Citizenship and Immigration Canada spokeswoman Nancy Caron said in an emailed statement. "These unfounded claims clog up our system for genuine refugees who are actually fleeing persecution."

It's a strikingly different stance from what Bruce Beyer saw when he found a safe haven in Canada and spent five years there after refusing induction into the Army during the Vietnam War.

"The word is definitely out in the anti-war community that going to Canada is not beneficial," said Beyer, of Buffalo, who returned to the United States in 1977 and has publicly supported the current resisters.

Canada's Immigration and Refugee Board does not track claim types and could not provide the number of claims made by American soldiers, spokesman Robert Gervais said. He said each case is decided on merits.

Robidoux estimated the number of claims filed at 45. She said about two dozen soldiers remain in the country while appealing decisions or pursuing other action. One of them, Rodney Watson, has sought sanctuary in a Vancouver church for nearly six years to avoid a second tour in Iraq.

Both Watson and Hart spoke out publicly against the war after arriving in Canada, and Hart believes his lengthy prison sentence was a direct result. Prosecutors sealed their desertion case against him with clips from anti-war rallies that captured him saying he had no plans to return.

Hart finally did, he said, after deciding with his wife, Jill, that it would be best for their son, now 13, to leave Canada on their own terms.

"We had kind of run the course of legal action to stay there, so we were pretty much just sitting there waiting for a deportation order to come down," said Hart, who was released from the prison complex at Fort Leavenworth, Kansas, in 2013 after serving 15 months.

Hart left his Fort Campbell, Kentucky, base in 2005, a month before he was to be sent to Iraq and after serving nearly a year in Kuwait in 2003. He now lives in Florida and is pursuing a nursing degree, helped by the G.I. Bill. He is seeking to have his bad conduct discharge -- a step up from dishonourable -- upgraded to other than honourable.

"Up until the second part of the Iraq War, I was pretty much a model soldier," said the sergeant, who had hoped his more than 10-year record would work in his favour upon his return, "but they didn't see it that way."

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Associated Press researcher Rhonda Shafner contributed to this report from New York.

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This story has been corrected to say conflicts in Iraq, not Iran, in third paragraph.