Iran has denied that its newly revealed uranium enrichment plant has any other purpose than producing electricity.
Western countries have accused that it was building a secret nuclear facility. President Obama has warned Iran to come clean on its nuclear programme or face tougher international sanctions.
Foreign Secretary David Miliband said he preferred diplomacy over force.
He said: ''no sane person looks at the military question of engagement with Iran with anything other than real concern that's why we always say we are 100% committed to the diplomatic track.
"I think it's very important that we stick to that, because the diplomatic track of engagement on the one hand and pressure on the other, has only now really been tried with the engagement of the Americans.''
Also interviewed on the programme, Mark Fitzpatrick, of the International Institute for Strategic Studies, considered Iran's nuclear ambitions.