The state of Texas was preparing Wednesday to execute a Mexican man sentenced to death in 1993, despite objections from human rights groups.
Roberto Moreno Ramos, 64, was due to be put to death by lethal injection at 6:00 pm (0000 GMT Thursday) in the penitentiary at Huntsville, Texas.
He was sentenced to death for bludgeoning his wife and two of their children, aged seven and three, with a sledgehammer in 1992 in the town of Progresso, near the Mexican border, where the family had been living for several years.
He hid the bodies under the tiling of the bathroom in their house and three days later married his mistress, who had no idea he was married. The bodies were only found two months later.
During his 25 years on death row, his lawyers have argued in vain that he suffers from brain damage and is bipolar.
Mexico, and its human rights defenders, have long decried the fact that Ramos was not informed that he could have access to legal aid from the Mexican consulate, a right guaranteed by the 1963 Geneva Convention of which the US is a signatory.
His execution would constitute "a flagrant violation of human rights and international law," said the Mexican government on Monday.
UN experts have said the execution would be "arbitrary" while the Inter-American Commission on Human Rights called on Texas to "fully respect its international human rights obligations."
In 2003, the Mexican government took Ramos' case, and the cases of 50 other Mexicans on death row in the United States, to the International Court of Justice in The Hague.
The court agreed that they had been denied their consular rights and ordered their cases to be re-examined.
But the US Supreme Court ruled in 2008 that US states were not obliged to implement decisions of the ICJ.
Since then, five Mexican nationals have been executed, all of them in Texas, according to the Death Penalty Information Center (DPIC).
Twenty people have been executed so far this year in the United States, 10 of them in Texas.