Image copyright Reuters Image caption A small group protested against trade deals outside Senate offices on Tuesday

Legislation key to US President Barack Obama's trade agenda has passed a key hurdle in the 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 bill is expected to pass a final vote in the Senate on Wednesday.

Tuesday's 60-37 vote - just barely meeting the required 60 vote threshold - is the result of the combined efforts of the White House and many congressional Republicans to push the bill through Congress, despite the opposition of many Democrats.

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.

However, opponents, including labour groups and many congressional Democrats, argue that previous global trade deals have resulted in large job losses in the US.

Image copyright Getty Images Image caption The Trans-Pacific Partnership would promote greater trade among 12 Pacific Rim nations

In the end, the bill cleared the procedural hurdle with the affirmative votes of 47 Republicans and 13 Democrats.

Specifically, the legislation would allow lawmakers to establish the objectives of trade negotiations, including the TPP, but would only allow them to vote yes-or-no on the final agreement. They would not be able to vote on the specific parts of the deal.

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.

On Tuesday, White House Press Secretary Josh Earnest, at his daily news briefing, urged members of Congress to pass the legislation.