FORT BLISS, Texas — U.S. authorities seized a record 316 metric tons of cocaine last year, top drug interdiction officials said Thursday as they credited Mexico's increasing cooperation with helping force drug traffickers to raise their prices and try new smuggling methods.

John Walters, director of the Office of National Drug Control Policy, said the record seizures have led to a 21 percent jump in the price of cocaine and a drop in the purity of the drug. The price of methamphetamine has jumped even more, he said, thanks to a crackdown on U.S. labs and Mexican authorities doing more to stop importation of precursor material.

Walters spoke Thursday at Fort Bliss, just outside El Paso, during a break in meetings with The Interdiction Committee, a multi-agency committee focused on stopping the flow of drugs into the U.S.

U.S. Coast Guard Adm. Thad Allen, commandant of the Coast Guard and chairman of the committee, said the rise in drug prices shows U.S. anti-drug efforts are working.

The average price of a pure gram of cocaine was $96.58 in early 2007 and rose to $117.22 by the end of the year, according to ONDCP, citing data from the U.S. Drug Enforcement Administration.

Allen also said traffickers have been forced to find new ways to try to sneak drugs in, including the use of submarine-like watercraft capable of carrying up to 10 tons of cocaine. The vessels, almost entirely submerged in water, have been spotted from South America to the Northern California coast.

"We have forced them to change," Allen said, adding that U.S. officials are also seeing liquid cocaine more often.

Federal officials said a key difference is an unprecedented level of cooperation between the U.S. and Mexico in combatting drug trafficking. Walters praised Mexican President Felipe Calderon's efforts to crack down on drug cartels.

"There has never been an investment like this before," Walters said, referring to a proposed U.S. aid package and the Mexican deployment of soldiers around the country. "We can't do this effectively without international partnerships."

Walters also reiterated his criticism of conditions some Senate leaders have proposed for the aid package, a three-year commitment that would provide about $1.4 billion to help Mexico in its ongoing fight against drug cartels and violent gangs.

"It needs to come in a form that is helpful," Walters said.

Some lawmakers have urged prohibition of U.S. funding for Mexican authorities accused of human rights, corruption or other criminal violations.

Increasing levels of violence among drug cartels, particularly in northern Mexican border cities where police are routinely being targeted by the cartels, are proof that the government's latest efforts are working, said Michael Braun, the DEA's chief of operations.

Braun said a similar spike in violence was seen in Colombia when the government there launched its offensive against powerful drug cartels.

"This is a classic turf war," Braun said. "An added dimension of the story is the commitment by President Calderon ... to take on these very powerful drug cartels. And when that happens, people, sometimes many people, are going to be killed."

But continued efforts by both governments will eventually lead to drops in crime in Mexico, Walters said.