Of particular concern is the damages apportionment provision, repeatedly condemned by the Chief Judge Michel of the Court of Appeals (CAFC).

High-tech companies, whose products may include hundreds of patented parts, want awards more closely tied to the specific patent that was infringed, rather than to the entire value of the product. Opponents say that would reduce damage awards and make it easier to infringe patents.

The unions oppose the current damages provision and a measure that would require the publication of patent applications within 18 months of submission, which they fear would make it easier for overseas competitors to copy U.S. inventions.

They received an unlikely boost last fall when a Chinese official, Yongshun Chen, a former judge, was quoted in the Chinese press as saying reform legislation "favors the infringers and burdens patentees more."

Bob Baugh, executive director of the AFL-CIO's industrial unions council, said Chen's comments "confirmed suspicions" that the legislation would lead to more counterfeiting of U.S. goods.

In a statement last month, the AFL-CIO's executive council said it is "ironic that, at a time when our nation is pressing China to upgrade its protection of intellectual property ... the United States would actively consider steps that could undermine the effectiveness of our patent protections."

The proposed legislation is heavily backed by IT mega-corporations.

Mark Holston, Hewlett-Packard's general counsel, said Tuesday the company is one of the largest U.S. patent holders and wouldn't support legislation that weakens patent protection.

Protection is always relative to what you can afford.