The United States is ready to slap fresh sanctions on Iran in the event international negotiations over its suspected nuclear weapons programme fail, a senior US Treasury Department official has said.

“This administration has demonstrated that it is committed to a diplomatic resolution of the international community’s issues with Iran,” Treasury Undersecretary Stuart Levey told the Senate Banking Committee.

“The world is now united in looking to Iran for a response.

If Iran does not live up to its obligations in this process, it alone will bear the responsibility for that outcome,” he said.

“Under these circumstances, the United States would be obliged to turn to strengthened sanctions,” said Levey, who as undersecretary for terrorism and financial intelligence oversees the department’s efforts to staunch the flow of funds to international terrorists and weapons of mass destruction proliferators.

“We are intensifying work with our allies and other partners to ensure that, if we must go down this path, we will do so with as much international support as possible,” said Levey.

“We will now wait to see whether Iran follows its constructive words with concrete action. If it does not, and if the president determines that additional measures are necessary, we will be ready to take action, ideally with our international partners.”

Levey told lawmakers that he was not in a position to provide details of the planned sanctions, although the department has completed work on them.

He added that sanctions already in place have borne fruit, and that the United States hope to exploit certain “economic vulnerabilities” in Iran.

“We will need to impose measures simultaneously in many different forms in order to be effective,” he said.

At the same hearing, the  Deputy Secretary of State James Steinberg described the administration’s approach as a “dual track strategy that presents a clear choice to Iran’s leaders.”

“They can negotiate in good faith, prove their willingness to address the concern of the international community, and in turn improve Iran’s standing in that community, or they can face increasing international isolation and pressure,” said Steinberg.

Meanwhile, the banking panel’s powerful chairman, Democratic Senator Christopher Dodd, said he was strongly in favour of ratcheting up the pressure on Tehran, and said he was crafting “comprehensive sanctions legislation” to be unveiled later this month.