The world's largest free trade zone is coming - what will it mean?

But critics question the alleged economic benefits of the deal - called the Transatlantic Trade and Investment Partnership (TTIP) - and say the inclusion of investor-state settlement dispute clauses will undermine democracy.

Negotiations began in July 2013 and the 9th round starts on April 20 in New York.

Karel De Gucht, a former EU commissioner for trade, said there is "a window of opportunity" to tie up the deal in 2015, or early 2016.

Talk of a trade deal between the EU and US has been around for decades but the catalyst for action was the economic crisis in 2008.

The powers-that-be decided that, because the EU-US trade relationship was already the biggest in the world, it could be a relatively cheap way of boosting both economies.

The idea is that, by removing trade barriers, it will make it easier and simpler to buy and sell goods and services.

The removal of tariffs and harmonising of regulatory frameworks could bring significant gains for the EU and the US, according to a report by the UK Centre for Economic Policy Research. (PDF)

It claims that the deal would boost the EU's economy by 119 billion euros a year and the US economy by 95 billion euros.

One key area where the US and EU differ is genetically modified foods.

The EU has some of the strictest GM regulations in the world and has authorised just 52 GM foods to date.

The US, on the other hand, is the largest commercial grower of GM crops in the world.

There is also concern that US producers will be able to sell their meat in European markets, even though it is produced to different standards. For example, chickens in the US are disinfected with chlorine, a practice banned in Europe.

The European Commission is negotiating the deal on behalf of the EU and its member states.

But there are concerns around transparency, despite the recent efforts made by the Commission.

The EC says the deal requires confidentiality, arguing that greater transparency would be like showing your hand to a rival card player.

TTIP critics say that, if financial services are included in the deal, it would force concessions in regulatory standards (PDF) at the expense of financial stability.

There were also concerns about the impact of the deal on Europe's film industry. However the European Commission insists the audio-visual sector, following objections from France, will not be part of the negotiations.