WASHINGTON - President Bush will propose tens of millions of dollars in assistance to Mexico to fight drug trafficking and violence that have ravaged that country and threaten to spill over into the United States, a Texas congressman said yesterday.

Democratic Rep. Henry Cuellar said Congress would come up with the final sum.

Bush "is going to make the proposal," Cuellar said, "but the president is going to have to work with us to do this."

The State Department declined to discuss specifics of the proposal because they are still being negotiated with Mexican authorities and lawmakers have not been fully briefed on the package.

Officials said they began to talk with President Felipe Calderon about new and substantial antidrug aid shortly after he took office in December.

He "has taken a brave and firm stance in fighting these drug cartels and fighting all the activities associated with the production and transit of illicit narcotics," State Department spokesman Sean McCormack said yesterday, "and we want to talk to him about how we can support that."

One antidrug official who requested anonymity because the package had not been completed said that negotiations were in an advanced stage and that it was hoped at least parts of the program could be announced when Bush and Calderon meet in Canada on Aug. 20 and 21.

U.S. antidrug officials have been impressed with Calderon's crackdown on drug traffickers since he took office. Through June, he sent more than 24,000 troops to areas plagued by drug violence.

Calderon has pushed the United States to take more responsibility in fighting the two countries' common drug problem, including doing more to stop the flow of illegal U.S. arms into Mexico and trying to combat the demand for drugs north of the border.

U.S. aid is touchy for many Mexicans, wary that the help could lead to interventions that violate sovereignty.