MEXICO CITY — Mexicans would be allowed to possess small amounts of cocaine, heroin, even ecstasy for their personal use under a bill approved by lawmakers that some worry could prove to be a lure to young Americans.

The bill now only needs President Vicente Fox's signature to become law and that does not appear to be an obstacle. His office said that decriminalizing drugs will free up police to focus on major dealers.

The Senate approved the bill Friday in the final hours of its closing session. Mexico's lower house had already endorsed the legislation.

The measure appeared to surprise U.S. officials. State Department spokeswoman Janelle Hironimus said the department was trying to get "more information" about it.

Some worried the law would increase drug addiction in Mexico and cause problems with the United States. Millions of American youths visit Mexico's beach resorts and border towns each year.

"A lot of Americans already come here to buy medications they can't get up there ... Just imagine, with heroin," said Ulisis Bon, a drug treatment expert in Tijuana, where heroin use is rampant.

In off-the-record chats and through their communications with U.S. officials, Mexican officials tried to depict the drug bill as a simple clarification of existing laws. But the changes are clear.

Currently, Mexican law leaves open the possibility of dropping charges against people caught with drugs if they can prove they are drug addicts and if an expert certifies they were caught with "the quantity necessary for personal use."

The new bill drops the "addict" requirement, allows "consumers" to have drugs, and sets out specific allowable quantities, which do not appear in the current law.

Those quantities are sometimes eye-popping: Mexicans would be allowed to posses 2.2 pounds of peyote, the button-sized hallucinogenic cactus used in some Indian religious ceremonies.

Police would no longer bother with possession of up to 25 milligrams of heroin, 5 grams of marijuana (about one-fifth of an ounce, or about four joints), or 0.5 grams of cocaine — the equivalent of about 4 "lines," or half the standard street-sale quantity.

However the bill stiffens penalties for trafficking and possession of drugs — even small quantities — by government employees or near schools, and maintains criminal penalties for drug sales.