David Cameron has warned that Iran is seeking to build an inter-continental missile that would threaten the west, as he urged Israel to allow time for sanctions to force the Iranians to change their strategic stance.

He was speaking after the cabinet was briefed for an hour by the national security adviser, Sir Kim Darroch, on the imminence of the threat to the UK posed by Iran.

It is the first time Cameron has made such an explicit warning that Iran could endanger UK security, and has faint echoes of the warnings from Tony Blair's government that Iraq could fire weapons of mass destruction with 45 minutes' notice.

It is understood that the government's National Security Council is also looking at potential reprisals in the UK if Israel were to launch a pre-emptive strike against an Iranian nuclear site. Critics accuse Iran of planning to use its enrichment of uranium for weapons. Cameron will be briefed by President Barack Obama next week on the US approach to any such strike when the two leaders meet in Washington.

Speaking to MPs on the Commons liaison committee, the prime minister said Tehran's ambitions were dangerous for the Middle East.

But Cameron also added that Iran "is a danger more broadly, not least because there are signs that the Iranians want to have some sort of inter-continental missile capability.

"We have to be clear this is a threat potentially much wider than just Israel and the region."

The Israeli prime minister, Binyamin Netanyahu, told an American Jewish group in Washington on Monday that diplomacy and sanctions had failed and that "none of us can afford to wait much longer" to act against Tehran.

On Tuesday six global powers agreed to resume negotiations with Iran on its nuclear programme, calling for "concrete and practical steps" to restore international trust in Tehran's stated intentions.

In a letter to Iran's chief nuclear negotiator, Saeed Jalili, the EU foreign policy chief, Lady Ashton, said the negotiations should restart as soon as possible, at a venue to be decided.

Writing on behalf of a negotiating group comprising the US, UK, France, Russia, China and Germany, Ashton said: "Our overall goal remains a comprehensive negotiated long-term solution which restores international confidence in the exclusively peaceful nature of Iran's nuclear programme, while respecting Iran's right to the peaceful use of nuclear energy consistent with the NPT [nuclear non-proliferation treaty]."

The last set of talks broke down in Istanbul in January last year. Western diplomats said Jalili refused at that meeting to negotiate over Iran's nuclear programme or any confidence-building measures previously discussed, such as an exchange of Iranian enriched uranium for foreign-made fuel rods for the Tehran research reactor.

At the meeting, the Iranian negotiator laid down preconditions for talks including the lifting of all sanctions and a guarantee that Iran could continue its nuclear programme, including the most controversial element, uranium enrichment.

Tehran says the programme is for purely peaceful purposes, but the west and Israel allege it is a front for an effort to build a nuclear arsenal, or at least establish the capacity to build a bomb at short notice.

Jalili's reply to Ashton was delivered in February, four months after her proposal, suggesting talks on "a spectrum of issues" including "Iran's nuclear issue".

French officials argued that in order to satisfy Israel that all was being done to resolve the nuclear crisis by peaceful means, the international response would have to make it absolutely clear that the talks would have to end with the "full implementation" of UN security council resolutions calling for the suspension of uranium enrichment. That language was spelt out in Ashton's latest letter.

A report by the International Atomic Energy Agency (IAEA), presented to the agency's board this week, said Iran had tripled its rate of production of 20%-enriched uranium – seen by the west as a particular proliferation threat – and reported that Iran had not co-operated with an inspection visit last month, refusing access to a sensitive military site known as Parchin.

Iran is thought to have already developed a ballistic missile which can travel approximately 1,200 miles. The International Atomic Energy Agency has asked Iran to explain evidence that it once worked on a missile payload design that could be used to deliver a nuclear warhead.

There is evidence that the Iranians and North Koreans cooperated in the past on missile technology. However, there is no proof of North Korean involvement in any payload design, nor is there conclusive proof that Iran itself has pursued the development of such a weapon.

Cameron stressed that Iran should not be seen as "a mini superpower" but as "a disastrous country" with mass unemployment and a dysfunctional economy.

He said he still believed the track of sanctions should be pursued, arguing EU-wide sanctions were causing dislocation to the Iranian foreign exchange position and "should not be sniffed at".

He said the next step was to get the Indians and Chinese to also refuse to buy Iranian oil.

"The more pressure we pile on Iran through sanctions the more incentive they have to take a different path – it is the best option we have".

The prime minister said that no plans were being laid at this stage to increase the UK military presence in the region.

• This article was amended on 9 adn 12 March 2012 because quotes attributed to David Cameron went farther than his words as spoken. Headings said, Iran 'seeking to build nuclear weapon', warns David Cameron; and Prime minister says Iran is planning an 'inter-continental nuclear weapon'. Story text said, David Cameron has warned that Iran is seeking to build an 'inter-continental nuclear weapon' that threatens the west. These have been corrected to conform with his remark about an intercontinental missile capability quoted elsewhere in the story. An assertion that Iran is working with North Korea to turn an existing Iranian missile into one that can accommodate a nuclear warhead has been replaced by a more detailed account. Finally, the original article mentioned possibility of a pre-emptive strike against an Iranian "nuclear weapons site". This has been changed to nuclear site.