GENEVA — The UN human rights office called Friday on the US state of Texas to spare the life of a Mexican death row inmate convicted of rape and murder, as there were questions about whether he had a fair trial.

Humberto Leal Garcia, 38, is scheduled to die in Texas on July 7, but Mexico maintains he was not given proper consular access, a violation of the Vienna Convention.

Rupert Colville, spokesman for the UN High Commissioner for Human Rights, pointed out that the governor of Texas "has the power to commute the sentence to life imprisonment."

"The High Commissioner has written to him directly requesting him to do so," he said.

"Over and above the normal UN position opposing the death penalty, this case raises particular concerns, as Mr Leal Garcia was not granted consular access, which, as a foreign national, is his right under Article 36 of the Vienna Convention on Consular Relations.

"The lack of consular assistance and advice raises concerns about whether or not Mr Leal Garcia?s right to a fair trial was fully upheld," added Colville.

In a separate statement, two UN experts also called for the the execution to be halted.

"If the scheduled execution of Mr Leal Garcia goes ahead, the United States government will have implemented a death penalty after a trial that did not comply with due process rights," said Christof Heyns, special rapporteur on extrajudicial killings.

"This will be tantamount to an arbitrary deprivation of life," he added, in the statement issued jointly with UN special rapporteur on torture Juan Mendez.