The PM said the UK would "move quickly" to enhance security
Gordon Brown has called a summit in London to discuss radicalisation in Yemen, after the alleged failed bomb attack on a US plane over Detroit.
No 10 said the 28 January event had support from Washington and the European Union, and Mr Brown aimed to attract Saudi Arabia and Gulf states.
Alleged plane bomber Umar Farouk Abdulmutallab is believed to have linked up with al-Qaeda in Yemen.
Mr Brown has ordered a UK airport security review following the attack.
The prime minister said the meeting would involve key international partners and be held alongside the conference on the future of Afghanistan, due to be held in London on the same day.
He said: "The international community must not deny Yemen the support it needs to tackle extremism.
"I have said before that Yemen - as both an incubator and potential safe haven for terrorism - presents a regional and global threat."
Mr Brown added that the UK had a £100m commitment to Yemen, making it one of the country's biggest donors, and was providing intelligence support.
On Tuesday, Yemen's Foreign Minister Abu Bakr al-Qirbi told the BBC that Yemen had the will and ability to deal with al-Qaeda, but needed more support from the West.
He added: "We need more training. We have to expand our counter terrorism units and this means providing them with the necessary training, military equipment, ways of transportation - we are very short of helicopters.
"The United States can do a lot, Britain can do a lot, the European Union can do a lot in that regard."
Downing Street said the aims of the conference would include identifying Yemen's counter-terrorism needs and discussing ways of tackling radicalisation through aid and reform.
Mark Pritchard MP, vice chairman of the Parliamentary Yemen Group, said: "Yemen is very close to becoming a failed state that is why other European government's need to do far more, and urgently, in supporting Britain's ongoing commitment to try and improve security and counter-terrorism expertise in country.
"If Yemen does become a failed State it will provide a safe haven for terrorists with close proximity to important shipping routes and neighbouring oil-producing Saudi Arabia. The stakes for the region and the West are very high indeed".
Announcing a review of existing security measures, Mr Brown said the UK would "move quickly" to enhance airport security after the "wake-up call" of the failed US plane attack on Christmas Day.
He added that advisers would report within days and full-body scanners would be among the new technologies considered.
Mr Brown also said the alleged plane bomber, Umar Farouk Abdulmutallab, who had studied in London, had joined forces with al-Qaeda in Yemen after leaving the UK.
A former close friend of Mr Abdulmutallab told the BBC he believes he was radicalised after leaving the country in 2008.
Qasim Rafiq knew the suspect for three years at University College London, and preceded him as president of its Islamic Society.
He says Mr Abdulmutallab had shown no signs of violent extremism while living in the UK.
Nigerian-born Mr Abdulmutallab is accused of trying to detonate a bomb on a flight as it came in to land on Christmas Day.
The 23-year-old allegedly attempted to ignite explosives stored in his underpants. He had flown from Lagos to Amsterdam before changing planes for a flight to Detroit.
US President Barack Obama has also ordered a review of air security, and Mr Brown said the UK would work alongside the US and other partners to "move things forward quickly".
Mr Brown said the UK had one of the "toughest borders in the world" and although Mr Abdulmutallab was on a watch-list and had not been allowed into Britain, it did not "lead us to any complacency".