TEHRAN, Iran — Iran's parliament authorized the government Tuesday to retaliate against countries that inspect cargo on Iranian ships and aircraft as part of new UN sanctions over its nuclear program.

Lawmakers, hoping to discourage compliance with a fourth round of Security Council penalties, passed a bill allowing the government to respond in kind, with cargo inspections of its own.

Last month's Security Council resolution calls on, but does not require, all countries to cooperate in cargo inspections if there are "reasonable grounds" to believe the items could contribute to the Iranian nuclear program, and any inspection must receive the consent of the ship's flag state.

The new sanctions, which also include financial penalties, were imposed because of Iran's refusal to halt uranium enrichment, a technology the United States and other world powers suspect Tehran is seeking to master as a possible pathway to nuclear weapons. Iran says it is only after nuclear power.

In Geneva, Iran's parliament Speaker Ari Larijani said his country's new law should serve notice that it accepts only the conditions in the Nuclear Nonproliferation Treaty, which grants signatories the right to develop peaceful nuclear energy as long as they do not acquire atomic weapons.

"There should be a balance between the obligations and the rights within the framework of the NPT," he told journalists through an interpreter. "If they ignore our rights, then they could expect us to ignore some of our obligations."

"If they want to act illegally and inspect Iran's ships, then we will retaliate," he said.

The Iranian bill also requires the government to maintain its limited level of cooperation with United Nations nuclear safeguards agreements. Iran, for example, refuses to allow surprise visits by UN nuclear inspectors.

Iran's uranium enrichment program is at the center of international concerns about its nuclear work because of the possibility it could be used to make weapons. At lower levels of processing, enriched uranium is suitable for making fuel for power plants. Iran recently increased its enrichment to a level of 20 per cent, which it says is needed for a medical research reactor.

That development, however, puts it much closer to being able to advance toward the 90 per cent level needed in weapons production.

The bill adopted Tuesday presses the government to continue enriching uranium to 20 per cent levels and to pursue self-sufficiency in nuclear fuel production.