An overwhelming majority of the US Senate urged President Barack Obama on Tuesday to impose "crippling sanctions" on Iran's financial system in a bid to hinder its suspect nuclear program.

"The time has come to impose crippling sanctions on Iran's financial system by cutting off the CBI," the Central Bank of Iran, 92 of the chamber's 100 members, Democrats and Republicans, wrote to Obama in a letter.

Republican Senator Mark Kirk and Democratic Senator Chuck Schumer led the effort, saying it was time to "increase the economic pressure" on Tehran with "a comprehensive strategy" to address the Islamic republic's defiance of global sanctions aimed at forcing it to freeze its uranium enrichment program.

"If our key allies are willing to join, we believe this step can be even more effective," the senators wrote.

Iran denies major Western powers' charges that it seeks nuclear weapons under cover of its civilian space and atomic energy programs, while pursuing ballistic missile technology that could let it strike faraway targets.

The senators charged that Iran's central bank "lies at the center of Iran's circumvention strategy" for ducking US and multilateral sanctions, which heavily target the country's financial and energy sectors.

"We urge you to strongly consider imposing US sanctions against the CBI and to encourage key allies to join us in this important action," they wrote.