But the discussions on the Transatlantic Trade and Investment Partnership, which both sides want completed by year-end, come amid rising anti-free trade talk in the US presidential election race and the threat that Britain could move to pull out of the 28-nation EU this year.
The week-long talks are the 13th round of negotiations on the TTIP pact since they began in July 2013. They have run well past the original target deadline of last October.
TTIP is billed as a free-trade and investment deal for the 21st century, focused heavily on harmonizing regulations and standards, lowering barriers on investment, opening access to government contracts and addressing new areas like data trade and consumer protections.
In the United States, politicians of both major parties battling to replace President Barack Obama in the November elections have taken to battering the TTIP's sister pact, the Trans-Pacific Partnership, already negotiated under Obama's lead and now awaiting ratification by 12 Pacific Rim nations.
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And in Europe there is deep public suspicion that TTIP will erode a wide range of social and consumer protections to the advantage of companies.
Obama said yesterday in Hanover, Germany, that the two sides need to keep pressing forward to complete an agreement by year-end.
The day before, tens of thousands of people marched through Hanover against TTIP.
German Economy Minister Sigmar Gabriel warned yesterday that the deal would fail if the United States refused to make concessions, notably on issues of European access to US public procurement contracts.
"They don't want to open their public tenders to European companies. For me, that goes against free trade," Gabriel told business newspaper Handelsblatt.