Hillary Clinton today vigorously defended President Obama’s recent overtures to Iran, insisting that the US would be in a better position to organise “crippling” international sanctions should diplomacy fail.

Giving her first congressional testimony on US foreign policy since becoming Secretary of State, Mrs Clinton said stopping Iran from acquiring a nuclear weapon was one of the Obama administration’s highest priorities.

“We actually believe that by following the diplomatic path we are on, we gain credibility and influence with a number of nations who would have to participate in order to make the sanctions regime as tight and as crippling as we would want it to be,” Mrs Clinton told the House Foreign Affairs Committee.

“We know the imperative of preventing Iran from obtaining nuclear weapons,” she added. “After years during which the United States basically sat on the sidelines, we are now a full partner” in international talks with Iran.

Iran said today that it welcomed “constructive” talks with world powers and the US, but added that it would press ahead with its programme to develop atomic energy.

Tehran insists its uranium enrichment programme is for civilian purposes; the West says Iran is seeking to develop a nuclear weapon.

The Iranian comments were in response to an invitation from the US, UK, China, France, Germany and Russia for a new round of talks about its nuclear programme. No date has been set.

If such talks fail, however, it is unclear whether the US would be able to persuade China and Russia, which have resisted harsher sanctions against Iran, to impose tougher penalties. Both are permanent members of the UN Security Council.

“We are deploying new approaches to the threat posed by Iran, and we’re doing so with our eyes wide open and with no illusions,” Mrs Clinton said.

She added: “It is going to be a more successful engagement if our partners around the world understand they must work with us,” including on consultations aimed at imposing tougher sanctions against Iran. “The fact that we are engaging ... actually gives us more leverage with other nations."

Times Recommends

• Google to digitise Iraqi artefacts
• Renault angers parents by naming new car Zoé
• Analysis: most lawless part of Philippines