But those remarks were belied by earlier comments from Mr. Hunt, the British foreign secretary, who described the developments in Iran as “unwelcome” and warned there would be consequences for Tehran if it failed to comply with the agreement.

Although both countries wanted to make sure that Iran would not develop a track to build a nuclear weapon, Mr. Hunt added, “It’s no secret we have a different approach on how best to achieve that.”

The Europeans have been working on a limited way around American sanctions that would allow European companies to do a kind of barter trade with Iran without using the dollar or ordinary banks. Set up by Germany, Britain and France, the mechanism, called Instex, or “Instrument in Support of Trade Exchanges,” is in its initial stages, and relied on Iran setting up a similar system, which happened only at the end of April.

But so far even Instex has only been seen as a way to trade in items not covered by American sanctions, including medical goods, food and humanitarian aid, and Mr. Pompeo indicated that nothing had changed on that front.

“We’ve talked with the U.K., Germany and France,” Mr. Pompeo said at the news conference. “There are provisions that allow humanitarian aid and certain products to get in the country. But when transactions go beyond that, there will be consequences.”

There is no indication that European companies, which do far more trade with the United States than with Iran, will want to use Instex and risk being punished somehow by Washington.