WASHINGTON — The United States, Europe and Russia responded with extreme skepticism to Iran’s announcement on Monday that it had reached an agreement to ship roughly half of its nuclear fuel to Turkey, saying they would continue to press for new sanctions against Tehran.

Nonetheless, officials from several countries said that the deal, negotiated with the leaders of Turkey and Brazil, was a deftly timed attempt to throw the sanctions effort off track.

The terms were similar to those of an accord made with the West last October that fell apart when Iran backtracked. Since then, Iran has added considerably to its stockpile of low-enriched uranium, meaning that it would keep on Iranian territory about half of its current supply — or about enough fuel for one nuclear weapon if it chose to make one. The earlier deal was attractive to Washington because it would have deprived Tehran of enough known fuel to make a weapon, leaving breathing space for negotiations.

Rejecting the new deal, however, could make President Obama appear to be blocking a potential compromise. And the deal shows how Brazil and Turkey, which for their own economic interests oppose sanctions, may derail a fragile international consensus to increase pressure on Iran.