The United States and the European Union launched negotiations for the world's most ambitious free-trade deal on Monday, promising thousands of new jobs and accelerated growth on both sides of the Atlantic.

Trade between Europe and the United States is worth almost $3 billion a day and a pact could boost both the EU and U.S. economies by more than $100 billion a year each - an attractive prospect after the devastating impact of Europe's debt crisis.

"This is a once in a generation prize and we are determined to seize it," said British Prime Minister David Cameron, flanked by U.S. President Barack Obama and the presidents of the European Commission and the European Council.

The first round of negotiations will take place in Washington in July, Obama said, speaking at the Group of Eight summit near the Northern Irish town of Enniskillen.

First considered three decades ago but knocked down by France in the 1990s, the idea of an EU-U.S. free-trade deal has gathered momentum as Brussels and Washington look to generate growth and China's rise prompts deeper Western integration.

The United States and the European Commission, the executive body of the 27-country European Union, hope for a free-trade deal by the end of 2014 - a tight deadline in complex international trade talks that usually take many years.

The European Union and the United States already account for about half the world's economic output and nearly a third of world trade, and bringing down the final barriers to trade could unleash billions of dollars in transatlantic business.

But France threatened to block the start of talks until the other 26 EU governments accepted on Friday its demand to shield movies and online entertainment from the might of Hollywood and Silicon Valley.

That kept Paris on board, but EU and U.S. officials have said that excluding any sector from the talks threatens the scope of comprehensive deal and could limit the economic gains.

Obama hinted at that in his remarks. "It is important that we get it right and that means resisting the temptation to downsize our ambitions or avoid tough issues just for the sake of getting a deal," he said.

The London-based Centre for Economic Policy Research estimates a pact - to be known as the Transatlantic Trade and Investment Partnership - could boost the EU economy by 119 billion euros ($159 billion) a year, and the U.S. economy by 95 billion euros.

However, a report commissioned by Germany's non-profit Bertelsmann Foundation and published on Monday, said the United States may benefit more than Europe. A deal could increase GDP per capita in the United States by 13 percent over the long term but by only 5 percent on average for the European Union, the study found.

Businesses on both sides would like an agreement in which a car tested for safety in the United States would not have to be tested again in Europe, and a drug deemed safe by Brussels would not have to be approved as well by the U.S. government.

Following the collapse of global trade talks in 2008, both the United States and Europe have sought to strike as many free-trade agreements as possible, and Brussels alone is negotiating with more than 80 countries.