TEHRAN, Iran— Iran vowed yesterday to expand its uranium enrichment, defying a U.N. Security Council deadline for it to suspend its nuclear activities by the end of the month or face the threat of political and economic sanctions.

Top nuclear negotiator Ali Larijani’s statement was Tehran’s first warning since the resolution passed that it could step up its atomic program. It suggested Iran is feeling emboldened in its main confrontation with the West, over its nuclear program, as Europe and America scramble to deal with the escalating violence between Israel and Lebanon-based Hezbollah militants.

“We will expand nuclear activities where required. It includes all nuclear technology including the string of centrifuges,” Mr. Larijani said, referring to the equipment Iran uses to enrich uranium, which can be used as fuel for a nuclear reactor or fissile material for an atomic warhead.

Mr. Larijani denounced the July 31 U.N. nuclear vote as “illegal” and said, “We reject this resolution.”

Mr. Larijani said Iran intends to meet Tehran’s previously announced goal of responding by August 22 to a package of incentives put forward in June by America and Western nations to entice Iran into suspending enrichment.

The United Nations said the sanctions threat in the deadline would be revoked if Iran accepts the package — but the resolution reflected Western impatience over the months Tehran has taken to respond to the offer.

Mr. Larijani said the deadline threat was “contrary” to the incentives package and blamed the West for damaging efforts for a diplomatic solution.

“We were expected to hold talks … to remove ambiguities … but they issued a resolution [at the U.N. Security Council) and killed it [talks]. They should explain why they damaged the path of dialogue,” he said.

Mr. Larijani insisted the U.N. had no right to require Iran suspend enrichment, saying his country has not violated any of its obligations under the Nuclear Nonproliferation treaty.