They spoke at a meeting of governors of the United Nations nuclear agency, a day after the UN Security Council said it was ready to tackle Western powers’ proposals for new sanctions on Iran, which China has so far resisted.

A diplomat in the closed-door International Atomic Energy Agency meeting said China’s ambassador reiterated that more negotiations, not sanctions against its major trade partner, must be pursued.

IAEA chief Yukiya Amano has reported to the agency’s 35-nation governing board that intelligence indicates Iran may be trying to develop a nuclear warhead.

Iran, which has branded Amano as incompetent and biased toward its Western critics, says the IAEA received adequate notice before the enrichment boost for what it says are wholly peaceful purposes.

Spain’s envoy to the IAEA, speaking as the EU’s current president, noted Amano’s complaint that Iran started refining uranium up to 20 percent last month without inspectors present, although the IAEA had asked Iran to wait until they were.

This violated Article 45 of Iran’s safeguards agreement with the IAEA, “which calls for notice of major changes ‘sufficiently in advance’,” the unusually hard-hitting EU statement said.

Washington’s IAEA ambassador agreed in remarks to reporters. The United States said Iran’s “cat-and-mouse game” with inspectors, its plan for 10 more enrichment sites and snubbing of an IAEA-brokered deal to swap enriched uranium for fuel for a medical isotope reactor would pave the way to stiffer sanctions.

“We hope that Iran will change its current course and seek the path of negotiations. Not doing so leaves the international community no choice but to pursue further, deeper sanctions to hold Iran accountable,” said US Ambassador Glyn Davies.

Western delegates challenged Iran’s assertion that enriching uranium to 20 percent purity was solely to make fuel for the reactor itself, rather than launching itself most of the way down the road to making bomb-grade nuclear fuel.

They said Iran lacked the fuel conversion technology and therefore could not hope to replenish the reactor’s imported Argentine fuel stock before it runs out later this year.

Iran is “choosing provocation over confidence-building and rhetorical defiance over the medical needs of its people,” Davies said, alluding to 850,000 Iranian cancer patients who Tehran says depend on isotopes made by the reactor.

The EU said Iran’s stated aim to massively expand enrichment despite successive UN Security Council resolutions demanding a suspension was “a further provocation and defiance.” “Iran’s ... apparent lack of interest in pursuing negotiations require a clear response, including through appropriate measures,” it said, referring to further sanctions.

Amano, defending himself against attacks by Iran and a developing nation bloc to which Tehran belongs, told governors on Monday his findings were “factual and absolutely impartial,” based on consistent, compelling intelligence from many sources.