WASHINGTON, Aug 5 - A U.S. senator has rejected a plan by the State Department to issue a report affirming Mexico is respecting human rights in its war against drug traffickers, which could delay release of millions of dollars in U.S. anti-narcotics aid, the Washington Post reported on Wednesday.

Citing U.S. officials and congressional sources, the Post said Senator Patrick Leahy, a Democrat who chairs a subcommittee that oversees foreign aid spending, told the State Department such a finding would contradict reports of human rights violations in the drug war.

The State Department had intended to send a favorable report on Mexico's human rights record ahead of President Barack Obama's visit to Guadalajara for a summit of North American leaders this weekend, the newspaper said, citing officials familiar with the report.

More than $100 million in U.S. aid to Mexico is at stake under the Merida Initiative, a three-year, $1.4 billion counter-narcotics package launched in 2007 under former President George W. Bush, the Post said.

The aid, aimed at helping Mexico crush the drug trade that has most of its market in the United States, is for uses such as training Mexico's police and buying helicopters and other equipment.

The law requires Congress to withhold 15 percent of most of the aid until the secretary of state reports that Mexico has made progress on human rights.

Mexican President Felipe Calderon has poured about $7 billion into a military crackdown on drug cartels that send some $40 billion worth of illegal drugs across the U.S. border each year.

Concerns have been raised in the U.S. Congress about possible human rights violations by Mexican troops in the crackdown.

The Post said State Department officials were considering rewriting the report before submitting it to Congress, probably after it reconvenes in September after its month-long summer recess