Democrats in the United States Senate have blocked a fast-track trade bill that would have given President Barack Obama the authority to finalise trade deals such as the Trans-Pacific Partnership and the Transatlantic Trade and Investment and Partnership with the EU.

In a dramatic rebuke to Mr Obama, Democrats have demanded additional protection for workers before they vote to even open debate on the bill giving new powers to the President. 

The bill would give him the authority to send any new international trade deal to Congress for a straight vote, without giving politicians the ability to change any part of the deal.

Republicans had worked with the President on the fast-track authority bill. 

Mr Obama views this authority as key to being able to negotiate international trade pacts with other countries.

Senate Democrats are seeking amendments to three other bills before they will pass this bill, but Republicans say there are very few extra concessions they are prepared to make.

Senate Majority Leader Mitch McConnell said that Republicans were prepared to attach funding for worker assistance programmes but could give no guarantees about other Democratic demands.