Tehran, Iran ? Iran’s president on Sunday ordered his atomic agency to significantly enrich the country’s stockpile of uranium, angering Western nations who want the Islamic republic to halt its nuclear program.

Mahmoud Ahmadinejad maintained, however, that Iran was also still willing to follow a U.N. plan to export its uranium abroad for further enrichment. Refining uranium produces nuclear fuel for a power plant but if carried out far enough can create material for a weapon.

The mixed messages from Tehran have infuriated the U.S. and its European allies, who claim Iran is only stalling for time as it attempts to build a nuclear weapon. U.S. Defense Secretary Robert Gates called for the international community to pressure Iran into abandoning its nuclear program.

German Defense Minister Karl-Theodor zu Guttenberg said: “Today’s statement shows that farce is being played out just like we have seen in the past, that the outstretched hand of the international community has not only not been taken but pushed back.”

The U.N.’s nuclear watchdog, the International Atomic Energy Agency, has been working on a compromise to defuse international tensions over Iran’s nuclear program. In October, the U.N. proposed that Tehran export its low-enriched uranium to Russia and France, who would return it a year later as enriched fuel rods that could be used to power Iran’s research reactor but couldn’t be further refined to make weapons-grade material.

Iran wants to enrich its stockpile of uranium to 20 percent, up from 3.5 percent, to power a research reactor to produce medical isotopes. But the international community has demanded a halt to all enrichment activity because the same process is used to produce weapons-grade material.

While material for a nuclear weapon is enriched to a level of 90 percent, just getting its stockpile to the 20 percent mark is a major step for the country’s nuclear program.

Achieving that level “would be going most of the rest of the way to weapon-grade uranium,” said David Albright, whose Washington-based Institute for Science and International Security tracks suspected proliferators.