Mongolia's permanent representative to the UN Od Och signed the joint declaration yesterday with Britain, China, France, Russia and the US to reaffirm the nuclear-weapon-free status of Mongolia as well as their security assurance to the country.
Mongolia had declared itself free of nuclear weapons 20 years ago but being a landlocked country between Russia and China, it could not join a regional bloc free of weapons.
The P5 powers did not want to recognise a one-country nuclear weapons free zone.
The agreement was reached after comprehensive talks between the parties here.
In a statement, UK's Foreign Office Minister Alistair Burt welcomed the declaration by the P5 and by Mongolia as a "further contribution to global and regional peace and security."
"By endorsing this declaration, the P5 agree to respect the nuclear weapon free status of Mongolia and not to contribute to any act that would violate it," he said.
Burt added that it is important to establish greater trust between Nuclear and Non-Nuclear Weapon States and is actively contributing to efforts to reduce the number of nuclear weapons worldwide.
The declaration states that the P5 will "respect the nuclear weapon free status of Mongolia and not to contribute to any act that would violate it," Britain's UN ambassador Mark Lyall Grant said.