Image copyright Getty Images

Legislation key to US President Barack Obama's trade agenda has been approved by the US Senate, just two weeks after it appeared to have failed.

The bill known as the Trade Promotion Authority (TPA), or more commonly "fast-track", makes it easier for presidents to negotiate trade deals.

Supporters see it as critical to the success of a 12-nation trade deal known as the Trans-Pacific Partnership (TPP).

The 60-38 vote was the product of rare Republican-White House collaboration.

The bill now awaits Mr Obama's signature.

The authority means that Congress may only vote up or down on finalised trade agreements, not amend them.

The Obama administration and many business organisations say the legislation is necessary so that trade negotiators can win lower trade barriers for US-made goods on international markets.

This fast-track bill brings the president a step closer to concluding the TPP deal with 11 other nations to remove or reduce barriers to trade and foreign investment.

How big a deal is TPP?

deal would include Japan, Malaysia, Vietnam, Singapore, Brunei, Australia, New Zealand, Canada, Mexico, Chile and Peru

have a collective population of about 800m - almost double that of the European Union's single market

the 12 nations are responsible for 40% of world trade

topics it covers include environmental protection, workers' rights, industry regulations

talks fiercely criticised for being too secretive

What is the Trans-Pacific Partnership?

There are also trade talks between the US and the EU that could be expedited.

Both deals have been opposed by trade unions and many Democrats, forcing the White House to forge an alliance with congressional Republicans.

"We were really pleased to see President Obama pursue an idea we've long believed in," said Senate Majority Leader Mitch McConnell, a long-time White House foe, who once said his top priority was making Mr Obama "a one-term president".

Image copyright EPA Image caption Senate Majority Leader Mitch McConnell, a long-time political nemesis of Mr Obama, thanked the president for his efforts

Senate Finance Committee Chairman Orrin Hatch, a Republican, said the bill was "the most important bill that will pass the Senate this year".

The bills's passage - made all but inevitable after it cleared a more stringent procedural hurdle on Tuesday - incensed many Democrats.

Speaking before Wednesday's vote, Senator Sherrod Brown said the bill would lead to "corporate handouts, worker sell-outs" in the way that he said the North American Free Trade Agreement (Nafta) and other deals have done over the past two decades.

Organised labour and environmental groups have been some of the most vocal critics of the trade agreements, saying that they harm the environment and endanger US jobs.

Image copyright AP Image caption Protests against 'fast track' have spread as far as California

However, Mr Obama and Republican leaders say that the agreements make it easier for US goods to reach global markets.

Less than two weeks ago, House Democrats and their leader, Rep Nancy Pelosi, turned against the bill in a vote that appeared to - at least temporarily - derail the president's trade agenda.

Following that, Republican leaders reworked elements of the bill and passed with large Republican and modest Democrat support.