The UN Security Council has slapped new sanctions on Iran over its suspect nuclear program as Western powers warned Tehran it faced becoming even more internationally isolated.

The council's 15 members on Saturday unanimously adopted Resolution 1747, co-sponsored by Britain, France and non-member Germany, broadening UN sanctions imposed on Iran in December for spurning repeated demands to suspend sensitive uranium enrichment.

"The unanimous adoption of this resolution reflects the international community's profound concern over Iran's nuclear program," said Britain's UN Ambassador Emyr Jones Parry, one of the sponsors.

The vote came amid an escalating diplomatic row between Iran and Britain over the fate of 15 British marines and sailors, who were seized in the Shatt al-Arab waterway between Iran and Iraq on Friday as they conducted "routine" anti-smuggling operations.

Permanent five plus Germany want negotiations

Foreign ministers of veto-wielding council members China, France, Russia, Britain and the United States plus non-member Germany also issued a statement proposing "further talks with the Islamic Republic of Iran to see if a mutually acceptable way can be found to open negotiations."

The six reaffirmed their commitment "to a negotiated solution that would address the international community's concerns."

But speaking at the United Nations after the vote, Iranian Foreign Minister Manouchehr Mottaki swiftly dismissed the UN sanctions as "unlawful" and "unjustifiable actions" orchestrated by a few of its members.

He did not respond to the six powers' offer of new talks.

As expected, the sanctions resolution was strongly supported by Israel, an arch-foe of Iran, which has repeatedly stated that a nuclear-armed Iran was unacceptable. "The international community should continue in this way to influence Iran and persuade the country to end its attempts to produce nuclear arms," Israeli government spokeswoman Miri Eisin told reporters.

The resolution, agreed after days of behind-the-scenes bargaining, blocks all Iranian arms exports and freezes the overseas assets of 28 additional officials and institutions linked to Iran's nuclear and ballistic missile programs.

It also restricts financial aid or loans to Tehran, and sets a fresh 60-day deadline for Iran to comply with UN demands or face "further appropriate measures."

Mottaki replaced in New York Iranian President Mahmoud Ahmadinejad, who late Friday canceled his plans to address the council, as Tehran blamed Washington for delaying his visa, a charge denied by US officials.

The minister reaffirmed Iran's right to conduct uranium enrichment as enshrined by the nuclear Non-Proliferation Treaty which Tehran signed.

Washington for its part welcomed the new sanctions, warning Tehran that it would face growing international isolation if it failed to comply with its obligations. "We are obviously very pleased by the strength of this resolution. It is a significant international rebuke to Iran and is a significant tightening of the international pressure on Iran," US Undersecretary of State Nicholas Burns told reporters.

He however said European Union envoys would now try to prod Iran into reconsidering its decision to continue with sensitive nuclear activities.

EU's Solana attempts to reopen discussions

EU foreign policy chief Javier Solana and other EU diplomats "would be in touch with the Iranian government in the days and weeks ahead to see if they might reconsider their obstinate refusal to renegotiate," he added.

"I have been asked by the countries that have been dealing most closely with Iran to make contact with Dr Ali Larijani in order to see whether we can find a route to negotiations," Solana said late Saturday.

"The door to negotiations is open; I hope we can together find a way to go through it," said the EU's top diplomat, who is taking part in European Union celebrations in Berlin marking the 50th anniversary of its founding treaty.

"We continue to be gravely concerned about Iran's program. The suspicion surrounding it affects negatively the stability in the Middle East," Solana added. "Our objective is to change all this. We want to see a successful Iran fully integrated into the international community. In particular, the European Union wants a better, closer relationship with Iran," said Solana.

"This is a country of huge potential and we are natural partners."

Talks between Iran, three European nations -- Germany, Britain and France -- Solana, and the International Atomic Energy Agency collapsed last year over Tehran's refusal to suspend uranium enrichment.

Meanwhile, Russia urged Iran to consider the implications of the sanctions and act accordingly. "We hope they (Iranians) will thoroughly study the statement of the foreign ministers which is very positive and invites Iran to engage in talks to find a mutually acceptable formula for negotiation," Russian Ambassador Vitaly Churkin said after the vote.

New sanctions pile on existing pressure

Iran has repeatedly denied allegations that it is trying to develop nuclear weapons, saying its uranium enrichment is purely to help meet the country's energy needs. Enriched uranium is the basic material for both military and civilian nuclear programs.

The draft resolution was worked out last week by the five veto-wielding permanent members -- Britain, China, France, Russia and the United States -- and Germany.

It builds on the December sanctions which included a ban on the sale of nuclear and ballistic missile-related materials to Iran, foreign travel restrictions on Iranians involved in sensitive atomic and ballistic missile work and a freeze on their overseas assets.

An annex to the new resolution details the diplomatic, economic and security incentives which the six powers presented to Iran last June to coax it into giving up uranium enrichment.