No other details were immediately available from the London meeting, but the major powers were expected to discuss imposing a travel ban on senior Iranian officials and restrictions on Iranian non-nuclear business.
UN sanctions were first imposed on Iran in December, barring the transfer of technology and know-how to its nuclear and missile programme.
The resolution said further measures could follow if Iran refused to halt enrichment by February 21.
Margaret Beckett, the UK's foreign secretary, said Iran was treading a "dangerous route" but that Western powers still wanted to negotiate.
"The steps that we have taken are reversible. There is nothing that we would like better than to be able to reverse them and no longer to have to continue with sanctions," she said.
Sean McCormack, a US state department spokesman, told reporters in Washington: "What we think should happen is a new UN security resolution ... or new incremental steps ... that would increase the diplomatic pressure on Iran."
Condoleezza Rice, the US secretary of state, promised direct talks with Iranian officials if Tehran halts its nuclear enrichment programme.
In response, Ari Larijani, Iran's top nuclear negotiator, said if the US made a formal request for talks, Tehran would respond positively but would not accept conditions placed on such discussions, Iran's official Islamic Republic News Agency (Irna) reported.
"Setting conditions means indicating the outcome of talks prior to holding them. Therefore, such a policy has not been answerable," Irna quoted Larijani as saying.
"Illegal and illogical"
But Iran says it is entitled to nuclear power to generate electricity and wants to negotiate with the Europeans and the US without giving up its right to enrich uranium.
"It is stubbornness and pride on Iran's part that has led to this impasse, and it can only lead to disaster for Iran"
Diom1982, Cork, Ireland
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A government spokesman in Tehran said the West's demand that Iran suspend enrichment was "illegal and illogical".
"Suspending uranium enrichment as a precondition for talks is an illegal and illogical demand and it is in contradiction with the Iranian nation's dignity," Gholamhossein Elham, an Iranian government spokesman, said.
"We are ready to preserve our legal rights through talks."
The meeting in London comes after the UN's nuclear watchdog confirmed Iran had ignored a deadline to suspend nuclear plans, with Mahmoud Ahmadinejad, Iran's president, saying Iran has "no reverse gear" on its programme.
Ahmadinejad was quoted by Iran's student news agency ISNA as saying on Sunday: "Iran has obtained the technology to produce nuclear fuel and Iran's move is like a train ... which has no brake and no reverse gear".
Manouchehr Mohammadi, one of the deputies to the foreign minister, was quoted as saying Iran was prepared "for any situation, even for war".
The diplomatic stand-off has also been described as "dangerous" by foreign ministers from seven Muslim states who met in Pakistan on Sunday.
"It is vital that all issues must be resolved through diplomacy and there must be no resort to use of force," said a statement agreed by the ministers representing Pakistan, Egypt, Jordan, Saudi Arabia, Turkey, Indonesia and Malaysia.
New Zealand and Australia have also urged Iran to be more transparent about its nuclear programme, with Helen Clark, New Zealand's prime minister, saying: "The problem is the lack of transparency. What the international community is asking for is transparency, open your facilities, be honest, give the information, don't play games ... The pressure has to go on for full disclosure."