In a verdant oasis in the deserts of northern Mexico, Republican challenger Mitt Romney's Mormon cousins mourned his presidential election defeat on Tuesday as a lost opportunity to pull the US economy out of the doldrums.

Romney's relatives in Mexico, whom he has never visited, had high hopes their clan's most famous son would win the keys to the White House, create jobs and boost trade.

When the former Massachusetts governor conceded defeat to Barack Obama on Wednesday, his Mexican brethren reacted with a mixture of dismay and stoic resignation, hailing his candidacy as a step forward for promoting understanding of the Mormon community.

"I'm just feeling very, very sad," said Virginia Romney, who was born on the same day as Romney in 1947, and is married to his Mexican second cousin Kent.

Despite rallying behind the Republican in the election, the Mexican Romneys were critical of the Republican line on immigration issues in the US, arguing that many Mexicans crossing the border illegally were just acting out of economic necessity.