Garza's execution, set for June 19, had been postponed by former President Clinton pending a review of a Justice Department study showing racial and geographical disparities in the federal death penalty system.

Clinton said the government should look at whether racism plays a role in the federal death penalty system before carrying out Garza's execution. No reviews have yet been released.

Lawyers for Garza, a Hispanic, say their client should be granted clemency because it's still an open question as to whether the sentence was the result of bias against minorities in federal death penalty prosecutions.

"To execute Mr. Garza in the face of this official recognition that additional study is necessary to determined whether bias exists in the administration of the federal death penalty would be unconscionable,'' said the petition, obtained by The Associated Press.

The document was filed Monday with the office of the U.S. pardon attorney at the Justice Department and with the White House counsel's office, said Gregory Wiercioch, an attorney for Garza.

The document is a supplemental memo to Garza's original clemency petition, which was filed last September.

The White House referred questions about the filing to the Department of Justice. The pardon attorney's office received the memo Monday, said Susan Dryden, a department spokeswoman. Garza's clemency petition is under review, she said.

"I believe the Garza case presents the Bush administration with the first test of its stated commitment to racial equality in criminal justice balanced against its support of the death penalty,'' Wiercioch said.

Garza, 44, was convicted of running a marijuana smuggling operations, killing one man and ordering the slayings of two others he thought were informants.

A Justice Department report released last fall said that between 1995 and 2000, U.S. attorneys recommended the death penalty be sought for 183 defendants, 26 percent of them whites and 74 percent minorities.

Then-Attorney General Janet Reno approved seeking death penalties for 159 of them, of which 28 percent were for whites and 72 percent for minorities. All involved murders.

Ultimately during this period, 20 defendants were sentenced to death - 20 percent white and 80 percent minorities. Most of the 20 inmates now on federal death row are minorities.

Attorney General John Ashcroft expects to make a statement soon, spokeswoman Chris Watney said.

Ashcroft supports the death penalty but has said the department should ensure that racial bias plays no role in the federal death penalty system.

The clemency petition also argues that Garza's sentence should be commuted because a human rights commission held that Garza's execution would violate his human rights under provisions of international law.

It also says Garza's death sentence violated due process because his sentencing jury should have been told that the alternative to the capital punishment was life in prison without the chance of parole.

Garza was convicted in 1993 under a 1988 federal law that imposes a death sentence for murder resulting from large-scale drug dealing. Prosecutors said he ran a marijuana operation that, from 1982 to 1992, brought tons of pot from Mexico for shipment to Louisiana and Michigan.

Garza has admitted accepted responsibility for the three murders, his lawyer said, but has complained that during the sentencing phase of his case the jury was allowed to hear testimony about alleged crimes in Mexico with which he was never charged.