The United States has long been frustrated with EU restrictions on U.S. farm products such as genetically modified (GMO) crops, poultry treated with chlorine washes and meat from animals fed with growth stimulant ractopamine.
In an early sign of EU reticence, Barroso said the negotiations would not compromise consumer health.
"We will not negotiate changes that we do not want of the basic rules on either side, be it on hormones or GMOs," he said.
The United States does not want a repeat of the Doha round of world trade talks, which began in 2001 and have never come to a conclusion, a point made by U.S. Vice President Joe Biden in a speech earlier this month about EU-U.S. negotiations.
"If we go down that road, we should try to do it on one tank of gas and avoid protracted rounds of negotiations," he said.
British Prime Minister David Cameron said in a statement he would use Britain's chairmanship of the G8 this year to help break down trade barriers and secure a comprehensive deal.
The EU-U.S. negotiation is unlikely to have any direct impact on the biggest and longest-running dispute in the WTO's history, the battle over subsidies for Airbus and Boeing. But it could help improve the mood and could be a prelude to a settlement in the aircraft dispute.
The EU too would like an agreement, but there are widely differing views between the broadly free-trade northern countries and the more hesitant southern countries hit hardest by the euro zone debt crisis.
Brussels is negotiating possible free-trade agreements with more than 80 countries, with some successes, such as a recent deal set to be struck with Singapore, but some talks, such as with India, showing no signs of ending.
Talks that began with Canada in 2009 have also failed to settle differences over agricultural exports, intellectual property and public procurement, despite two high-level efforts to break the deadlock.
(Reporting By Philip Blenkinsop, Robert-Jan Bartunek, Adrian Croft and Ethan Bilby; Additional reporting by Tom Miles in Geneva; Editing by Peter Graff)