The US Senate is within sight of passing major trade legislation and giving president George W Bush the trade negotiating authority that he has sought since his first days in office.

Senators were voting on Wednesday to shut off debate and move to a conclusion on the trade bill, a package that both restores "fast track" trade-negotiating authority to the president after an eight-year lapse and extends new benefits to workers who lose their jobs because of imports.

Supporters said they were confident of a strong final vote, which could occur late on Wednesday or Thursday.

That confidence came after the Senate rejected three amendments on Tuesday that could have undermined the delicate coalition between Republicans favouring free trade agreements and Democrats wanting assurances that labour would be protected from the fallout of those agreements.

The defeated amendments sought to provided low-interest loans to help workers hurt by foreign trade keep up with their mortgage payments for a year, extend health care benefits to steelworkers forced into retirement when their import-hit plants go out of business, and change a provision in the North American Free Trade Agreement that some lawmakers said has given legal advantages to foreign investors claiming that US environmental and public health laws hurt their businesses.

The trade bill gives the president the "fast-track" authority to negotiate trade accords that Congress can approve or reject but cannot change. Bush says he must have this authority if the United States is to take the lead in a new round of World Trade Organisation talks.

The bill also extends a 10-year-old programme, which recently lapsed, giving low tariffs to the Andean countries of Colombia, Peru, Bolivia and Ecuador as a means of boosting their economies and reducing their dependence on illegal drug production.

The Senate still must reconcile any bill it passes with the trade bill passed by the House of Representatives in December on a 215-214 vote. That narrow victory came after Republican leaders promised lawmakers from states with a large textile sector that Congress would take steps to protect the industry.