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 onto a sweeping defense spending bill being debated by the chamber, passed 94-0 and should sail through the House of Representatives.

Senator Robert Menendez introduced the measure 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 world community by refusing to slow uranium enrichment, 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."

The vote came on the same day a defiant Iran denied it was pursuing nuclear weapons and threatened to withdraw from the nuclear Non-Proliferation Treaty, which aims to stop the spread of atomic weapons.

Meanwhile, the P5+1 powers -- the United States, China, Russia, Britain, France and Germany -- said after a meeting in Brussels last week that they want talks with Iran "as soon as possible." This may happen as early as December.

Building on the US sanctions passed last year, the new amendment would designate Iran's energy, port, shipping and ship-building sectors as "entities of proliferation" because they "support and fund Iran's proliferation activities."

Under the new rules, the United States would sanction anyone selling or supplying certain commodities to Iran -- including graphite, aluminum, steel, and some industrial software -- that are relevant to the country's ship-building and nuclear sectors.

Despite tough US and European sanctions, Tehran has been able to bypass certain restrictions by accepting payment in forms like gold for certain exports.

The Menendez amendment targets such circumventions by seeking to prevent Iran's central bank from receiving payment in precious metals.

The sanctions would also designate the Islamic Republic of Iran Broadcasting and its president as "human rights abusers" for airing forced televised confessions and show trials.

Senator John McCain offered his blunt assessment of the need for expanded sanctions to counter Iran's intentions.

"The screws need to be tightened," the Republican told the Senate 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."

AIPAC, the pro-Israel lobby in Washington, praised the amendment as a way to "significantly ratchet up pressure on Iran," and pointed to earlier sanctions which have led to an 80-percent loss in the value of Iran's currency and a 50-percent slash in the country's oil exports.

But the National Iranian American Council saw the new sanctions as a dangerous step toward "a military endgame" and one that would "undercut their aspirations for democracy and human rights."

"Unbending sanctions do not buttress negotiations, they make diplomacy impossible and war inevitable," said NIAC Policy Director Jamal Abdi.

The defense spending bill would have to be reconciled with the House version passed in July, and the Republican-led House has been highly supportive of previous Menendez sanctions legislation against Iran.