It also would require importers to declare the species and country of origin for imports of wood and many plants, and would empower the government to seize suspect shipments and prosecute timber smugglers.

According to the Environmental Investigation Agency, 10 percent of all US imports of wood products in 2006 could be traced back to illegally logged timber, which can include wood harvested from a foreign country's national parks or shipped in violation of export restrictions .

"This is the first time any country in the world has prohibited import of illegally logged products," said Alexander von Bismarck, the group's executive director.

"Companies around the world are going to need to immediately change their operations in order to have a high level of confidence in who they're buying from," he said.

Rep. Earl Blumenauer, an Oregon Democrat who championed the measure in the House of Representatives, said illegal logging cost the US forest products industry more than $1 billion a year.

"Not only does illegal logging threaten some of the world's richest and most vulnerable forests, but it leads to serious human rights violations," Blumenauer said in a statement.

President George W. Bush has promised to veto the $290-billion farm bill, which the administration says is a "bloated, earmark-laden" measure that fails to truly reform crop subsidies and promises new problems with trade partners.

But after overwhelming support in votes this week, Congress looks set to override that veto.