Tehran, Iran ? Iran’s hard-line president said Tuesday that the country “has joined the club of nuclear countries” by successfully enriching uranium for the first time – a key process in what Iran maintains is a peaceful energy program.

The announcement from President Mahmoud Ahmadinejad was certain to heighten international tensions surrounding Iran’s nuclear program. The U.N. Security Council has demanded that Iran stop all enrichment by April 28 because of suspicions the program is designed to make nuclear weapons.

Ahmadinejad warned the West that trying to force it to abandon uranium enrichment would “cause an everlasting hatred in the hearts of Iranians.”

The head of the U.N. nuclear watchdog agency, Mohamed ElBaradei, was heading to Iran today for talks aimed at resolving the standoff. The timing of the announcement suggested Iran wanted to present him with a fait accompli and argue that it cannot be expected to entirely give up a program showing progress.

Former President Hashemi Rafsanjani, a powerful member of Iran’s ruling clerical regime, said the breakthrough means ElBaradei “faces new circumstances.”

The White House, which is pressing for U.N. sanctions against Iran, said the enrichment claims “show that Iran is moving in the wrong direction.”

“Defiant statements and actions only further isolate the regime from the rest of the world,” said White House spokesman Scott McClellan.

Britain’s Foreign Office issued a statement reiterating the U.N. call for a halt to enrichment work and warned that “if Iran does not comply, the Security Council will revisit the issue.”

The Iranian enrichment announcement “is not particularly helpful,” it said.

Uranium enrichment can produce either fuel for a nuclear energy reactor – as Iran says it seeks – or the material needed for an atomic warhead.

Tuesday’s announcement does not mean Iran is immediately capable of doing either. So far it has succeeded only in getting a series of 164 centrifuges to work in the enrichment process. Thousands of centrifuges are needed for a workable program.

But successfully carrying out the highly complicated and delicate process even on a small scale would be a breakthrough, and Iran’s nuclear chief said the program would be expanded to 3,000 centrifuges by the end of the year.

Ahmadinejad announced it at a nationally televised ceremony clearly aimed at drumming up popular Iranian support for the nuclear program. He addressed an audience that included top military commanders and clerics in an ornate hall in one of Iran’s holiest cities, Mashhad. Before he spoke, screens on the stage showed footage of nuclear facilities and scientists at work.

“At this historic moment, with the blessings of God Almighty and the efforts made by our scientists, I declare here that the laboratory-scale nuclear fuel cycle has been completed and young scientists produced enriched uranium needed to the degree for nuclear power plants Sunday,” Ahmadinejad said.

“I formally declare that Iran has joined the club of nuclear countries,” he said. The crowd broke into cheers of “Allahu akbar,” or “God is great.”