"They expressed concern that the bill would undermine individual privacy," Corrigan says. "With each step in the process, people become a little more educated. We hope that when it heads into (a future Senate-House conference committee), we can strip that section out."

Last December, the ACLU sent a letter to Congress saying that: "People in the United States have an expectation of privacy in the mail they send to friends, family or business associates abroad. The Customs Service's interest in confiscating illegal weapons' shipments, drugs or other contraband is adequately protected by its ability to secure a search warrant when it has probable cause."

In the Senate, a similar bill with identical mail-opening language is waiting for a floor vote, which is likely to happen as early as this week.

Democratic senators Jon Corzine (New Jersey) and Dianne Feinstein (California) are expected to introduce amendments to delete the mail-surveillance sections.

Other opposition to the mail-surveillance proposals comes from industry groups. The Direct Marketing Association says "this would be the first time since Ben Franklin created the Postal Service that seizure and searches, without warrants, of outbound international mail would be allowed."