The US Senate unanimously approved new economic sanctions Friday aimed at further crippling Iran's energy, shipping and port sectors, a year after Congress passed tough restrictions against Tehran.

The amendment, tacked on to a sweeping defense spending bill being debated by the chamber, passed 94-0, and should sail through the House of Representatives.

It was introduced by Senator Robert Menendez out of concern that Iran was pressing ahead with its nuclear weapons drive despite earlier sanctions that had been hailed as the toughest-ever against the Islamic republic.

"Yes, our sanctions are having a significant impact, but Iran continues their work to develop nuclear weapons," said Menendez, a Democrat.

He cited last week's report by the International Atomic Energy Agency that Iran continues to defy the United Nations and the world community by refusing to slow down enrichment facilities, denying access to inspectors, and conducting live tests of conventional explosives that could be used to detonate a nuclear weapon.

"By passing these additional measures ending sales to and transactions with Iranian sectors that support proliferation -- energy, shipping, ship-building and port sectors as well as with anyone on our specially designed national list -- we will send a message to Iran that they can't just try to wait us out."

Senator John McCain offered his characteristically blunt assessment of Iran's intentions, and the need for expanded sanctions.

"The screws need to be tightened," he said on the Senate floor just before the vote. "The centrifuges are still spinning in Tehran."

McCain said the new sanctions "can -- I emphasize can -- lead to a way to prevent a conflagration in the Middle East."