BEIJING - China on Friday urged Iran to give a "serious response" to a UN Security Council resolution that imposed sanctions on Tehran for refusing to suspend uranium enrichment.

Iran's top nuclear envoy, however, warned that Tehran's commitment to the peaceful use of nuclear technology will change if the country is threatened.

The negotiator, Ali Larijani, was in Beijing for a two-day visit and gave Chinese President Hu Jintao a letter from Iranian President Mahmoud Ahmadinejad.

Larijani and Hu discussed the UN sanctions, which bar all countries from selling materials and technology to Iran that could contribute to its nuclear and missile programs. The resolution, passed last month, also froze the assets of 10 Iranian companies and 12 individuals related to those programs.

If Iran refuses to comply with the demand to suspend uranium enrichment within 60 days, the resolution warns Tehran that the council will adopt further nonmilitary sanctions.

The sanctions reflect "the shared concerns of the international community over the Iranian nuclear issue, and we hope Iran could make a serious response to the resolution," Hu told Larijani, according to China's official Xinhua news agency.

Hu added that "China continues to believe the Iranian nuclear issue should be resolved through diplomatic negotiation."

In Tehran, Ahmadinejad said Friday that sanctions won't stop Iran from enriching uranium, state-run television reported.

"Iran will stand up to coercion. ... All Iranians stand united to defend their nuclear rights," state-run TV quoted him as saying.

"Enemies have assumed that they can prevent the progress of the Iranian nation through psychological war and issuing resolutions, but they will be defeated," Ahmadinejad was quoted as saying on state-run TV.

While the United States has led the drive to stop Iran from enriching uranium -- a process that produces the material for either nuclear reactors or weapons -- it compromised on the sanctions to win the support of China and Russia, both veto-wielding members of the Security Council who have strong trade ties with Tehran.

Larijani indicated that China's decision to support the resolution has not hurt ties between the two sides, calling them "long-term and long-lasting."

"Countries who have strategic long-term relationships will not change their strategic relationships because of tactical issues," he said at a news conference.

He added in reference to Washington: "We know who is really responsible, who is really behind the sanctions and nobody else can be blamed for this."

Iran has denied that it seeks to build atomic weapons, saying its nuclear program is limited to the generation of electricity, a stance Larijani reiterated.

"We oppose obtaining nuclear weapons and we will peacefully use nuclear technology under the framework of the Nonproliferation Treaty," he said.

"But," he warned, "if we are threatened, the situation may change."

In another show of defiance, Iranian Vice President Gholamreza Aghazadeh, who also heads the Atomic Energy Organization of Iran, announced that Tehran has produced and stored 250 tons of uranium hexaflouride gas, the feedstock for enrichment, state-run TV reported.

The hexaflouride gas, or UF-6, is being stored in underground tunnels at a nuclear facility in Isfahan to protect it from any possible attack.

"Today, we have produced more than 250 tons of UF-6. Should you visit Isfahan, you will see we have constructed tunnels that are almost unique in the world," state-run TV quoted Aghazadeh as saying.

The central Iranian cities of Isfahan and Natanz house the heart of the country's nuclear program. In Isfahan, a conversion facility reprocesses raw uranium, known as yellowcake, into uranium hexaflouride gas. The gas is then taken to Natanz and fed into the centrifuges for enrichment.

Iran has said it is moving toward large-scale uranium enrichment involving 3,000 centrifuges and plans to later expand this to 54,000 centrifuges. Centrifuges spin uranium gas into enriched material, which at low levels is used to produce nuclear fuel to generate electricity. But further enrichment makes it suitable for use in building nuclear weapons.

Iran has claimed to enrich small amounts of uranium at the low percentages needed for fuel-grade uranium, as opposed to weapons-grade enriched uranium, which must be enriched at levels above 90 percent. U.S. intelligence agencies have estimated that Iran might be able to develop a nuclear weapon in four to 10 years.

Aghazadeh confirmed in April 2006 that Iran has produced 110 tons of uranium hexaflouride gas. Experts say that amount would be enough to produce up to 20 nuclear bombs if Iran was to divert its civilian nuclear program into making weapons.