WASHINGTON -- Two federal agencies are being faulted for not coordinating their efforts against border gunrunners, a failure one lawmaker says made it easier for Mexican drug cartels to smuggle illegal weapons from the United States.

The Government Accountability Office criticized Immigration and Customs Enforcement and the Bureau of Alcohol, Tobacco, Firearms and Explosives for not working together to stop the flow of guns into Mexico.

In testimony prepared for a House subcommittee hearing, the GAO noted that the two agencies only recently stepped up their coordination with each other and with their Mexican counterparts to stop gunrunning along the border.

Rep. Eliot Engel, who chairs the subcommittee, said there should have been an anti-gunrunning strategy in place since October 2007, when the U.S. and Mexico agreed to the joint cartel-fighting Merida initiative.

"It is mind-boggling that for a year and a half, we have had no interagency strategy to address this major problem, but instead have relied on uncoordinated efforts by a variety of agencies," Engel, a Democrat, said in a statement.

Engel said the firearms flowing illegally from the U.S. into Mexico have made the drug cartels' jobs easier.

Engel's subcommittee was to meet on Thursday, but was delayed by other House business.

ICE spokeswoman Kelly Nantel said the two agencies pride themselves "on the strength of our relationships with law enforcement partners at every level and throughout the country."

Nantel said, "The Southwest Border is clearly one of the most important areas where we rely on these relationships to improve safety and security."

Citing ATF data, investigator Jess T. Ford said that over the past three years, more than 90 percent of the firearms traced after being seized in Mexico have come from the U.S. The figure is slightly less over a five-year period.

"While it is impossible to know how many firearms are illegally trafficked into Mexico in a given year, over 20,000, or around 87 percent, of firearms seized by Mexican authorities and traced over the past five years originated in the United States," the GAO's Ford said in testimony prepared for Congress.

The GAO is the investigative arm of Congress.