WASHINGTON (AP) ― The chief negotiators in new U.S.-European trade talks were upbeat Friday as the first round came to a close, saying tensions over secret American surveillance of European diplomats did not cloud the weeklong session.

The American negotiator Daniel Mullaney and his European Union counterpart Ignacio Garcia-Bercero told a news conference in Washington that some of the most difficult challenges they see ahead are in removing regulations that hinder trans-Atlantic trade.

The two economic powerhouses aim to seal a sweeping agreement that will remove most tariffs and other barriers to trade in order to boost jobs and growth. The first round of talks began on Monday and was ending on Friday.

Mullaney said America’s “overarching priority is to promote U.S. economic interests and to provide increased opportunities for American workers, businesses farmers and ranchers, and we are very optimistic about our prospects.”

Garcia-Bercero said the first round had been productive.

“Our first objective has been met,” he said. “We had a substantive round of talks covering the full range of topics that we intend to cover in this agreement. Both of us see this agreement as having the potential to deliver something that will be transformative for our economies in terms of market access, in terms of regulatory compatibility and in terms of rule-making.”

Mullaney noted the two economies are already hugely integrated with almost $3 billion in trade in goods and services every day, nearly $4 trillion in mutual foreign direct investment and a combined base of about 800 million consumers.

The launch of the talks last month during President Barack Obama’s visit to Europe almost snagged on French demands for a delay. The demands were in response to revelations that the U.S. had spied on European diplomats.

However Mullaney said this issue did not even arise in their talks.

“Those conversations are taking place in another channel so those topics did not come up among the trade negotiators this week,” he said.

The negotiating teams are grappling with how to reduce a host of regulations that obstruct trade such as Europe’s tight standards on imports of American genetically modified foods and meat that has been washed with chemicals.

Mullaney also addressed complaints from activists that the talks are not transparent enough because negotiating texts are not being released. He said there had been a number of sessions for activists and others to present their views to the teams and the negotiators were considering other ways to open up the process.

There were signs of diverging positions on a proposed mechanism in the trade deal known as “investor-state dispute resolution.”

The U.S. wants the provision, which would allow multinational companies to challenge a range of U.S. or European regulations in international courts.

Some activist groups have expressed alarm over the provision. They said it would elevate corporations to the level of sovereign states and allow them to challenge policies and laws that could cut into their profits.

Mullaney said the U.S. sees value in protecting investors and ensuring they have a fair, transparent and non-discriminatory process for settling disputes. Garcia-Bercero stressed the importance of protecting regulators and letting them do their jobs.