Michael Froman, with Trade Commissioner Cecilia Malmström | EPA Froman tells UK: No to EU means no to trade deal The Americans are ‘not in the market’ to negotiate a bilateral trade deal with Britain, Obama’s trade rep said.

The United States' trade representative just slammed Britain's Out crowd.

Michael Froman, U.S. trade representative, said the U.S. is "not particularly in the market for free trade agreements with individual countries."

"I think it's absolutely clear that Britain has a greater voice at the trade table being part of the EU, being part of a larger economic entity," Froman told the news agency Reuters, adding that European Union membership gives the United Kingdom more leverage in negotiations.

The statements come as a slap in the face for campaigners in Britain who are making the case for leaving the European Union. The "Better Off Out" campaign lists "freedom to make better trade deals with other nations" as the first reason to leave the EU.

The Obama administration has focused on wrapping up multilateral trade deals like TTIP (with the EU) and TPP (with Pacific partners). The Americans hope to finalize the deal with Europe before President Obama leaves office, an official said last week.

"We're building platforms ... that other countries can join over time," Froman argued Wednesday. If Britain leaves the EU "they would be subject to the same tariffs, and other trade-related measures, as China, or Brazil or India," he said.

The United Kingdom's largest trade partner is the EU; the U.S. is its second-largest partner.