WASHINGTON – House Republicans tentatively agreed Thursday to prohibit Customs agents from seizing prescription drugs that Americans buy in Canada and bring back into the United States.

The deal would let Americans carry up to a 90-day supply of medication back to the U.S. from Canada without being stopped by Customs agents, House and Senate Republicans said. But it would not let Americans purchase cheaper prescriptions over the Internet or by mail order, officials said.

“This really breaks the dam, and it shows that it’s only a matter of time before we pass a full-blown reimportation bill,” said Sen. David Vitter, R-La., who led the fight in the Senate to prohibit the Homeland Security Department from seizing prescription drugs being carried over the border. U.S. Customs and Border Protection is an arm of the Homeland Security Department.

Vitter acknowledged that sales of drugs through mail order or through the Internet is significant. But, he added, “I think support for that is going to continue and going to continue to grow, no matter what this bill says or doesn’t say.”

Both Presidents Bush and Clinton have rejected repeated congressional efforts to lift the ban on prescription imports. Medications are generally cheaper in Canada because of government price controls.

While importing drugs into the United States is illegal, the Food and Drug Administration generally has not stopped small amounts of medicine purchased for personal use. But Customs officials began intercepting imported controlled substances two years ago and prescription drugs since last November. Since then, Customs and Border Protection agents have seized more than 34,000 packages of drugs coming into the country.

The pre-election controversy over the new rule threatened to split House GOP leadership who oppose lifting the import ban and rank-and-file Republican lawmakers who want to help elderly voters buy cheaper drugs.

However, many Customs agents already allow prescription drugs into the U.S. from Canada because they don’t rigorously search people and cars for them.

Democrats who pushed for broader access to imported drugs accused Republicans of trying to “blow smoke to the voters about cheaper prescription prices when it really doesn’t do much of anything,” said Dan McLaughlin, spokesman for Sen. Bill Nelson, D-Fla. Earlier this year, Nelson sponsored legislation to prevent Customs agents from seizing mailed medication after he began getting complaints from seniors in his state.

“I think you could call this agreement in the House a very small advance and certainly we’ll take it, but it’s no place that we can stop and certainly isn’t enough to be satisfied with,” McLaughlin said. “It really doesn’t help very many people.”

Opponents said importing drugs that do not have FDA approval could be unsafe for consumers. The FDA says it cannot guarantee the safety of imported drugs.

Representatives for the pharmaceutical industry said Canadian Internet pharmacies, for example, have been known to sell fake and potentially unsafe medicines to unknowing American consumers through other countries.

“Americans should look at much safer alternatives that already exist and are proving to be incredibly effective here at home,” said Ken Johnson, senior vice president for the Pharmaceutical Research and Manufacturers of America, or PhRMA.

According to the Congressional Budget Office, brand-name drugs cost, on average, 35 to 55 percent less in other industrialized nations than they do in the United States. Supporters of importing drugs contend that the U.S. is subsidizing the cost of medicine for the rest of the world.

Associated Press writer Kevin Freking contributed to this report.