* Tightens the noose around energy, shipping sectors
* Oil exceptions would continue
* Natural gas sales allowed only if revenues used for trade
* Sanctions aimed at ending Turkey-Iran "gold for gas"
WASHINGTON, Nov 29 (Reuters) - The U.S. Senate is set to consider a broader set of economic sanctions on Iran's energy, port, shipping and shipbuilding sectors, as lawmakers look for new ways to pressure Tehran to stop efforts to enrich uranium to levels that could be used in weapons.
The new package also includes measures to stop the flow of gold from Turkey into Iran, Senate aides confirmed, trade that has helped Tehran manage its economy in the face of Western financial sanctions.
It is the third time in a year that U.S. lawmakers have looked for new ways to cut off revenues they believe fund Iran's nuclear program, which Tehran has said is strictly for civilian purposes.
The sanctions come as the United Nations' nuclear chief said his agency has made no progress in its year-long push to investigate whether Iran has worked on developing an atomic bomb.
Iran's economy has been badly damaged by sanctions by the United States and European Union, but Iran has not slowed its program, said Senator Robert Menendez, a New Jersey Democrat who helped craft the new proposal.
"Our message is clear: the window is closing. The time for the waiting game is over," Menendez said on the Senate floor.
The new sanctions were filed as an amendment to an annual defense policy bill. Senators debated other parts of the massive bill late into Thursday night and were expected to consider the Iran sanctions measure on Friday morning.
If accepted, the proposal would become part of the annual defense policy bill, which must be approved by the Senate and House of Representatives before it would be given to President Barack Obama to sign into law.
Republican Senator Mark Kirk of Illinois, who co-authored the package, said in a statement the sanctions would turn up pressure on Iran's government. Kirk and Menendez last year championed new sanctions that curbed Iran's oil exports.
"We have a responsibility to do everything in our power to put crippling pressure on the Iranian government, and passing these new sanctions is absolutely critical to that effort," said Senator Joseph Lieberman of Connecticut, an independent, who co-sponsored the new bill.
ENDS 'GAS FOR GOLD'
The package includes measures designed to stop the flow of gold from Turkey to Iran, said Mark Dubowitz, the head of the Foundation for Defense of Democracies.
Ankara relies on natural gas from Iran and has been paying for it using lira. Banking sanctions make it difficult for Iran to transfer money.
Tehran has used the lira to buy Turkish gold. Couriers carry the gold to Dubai and from there it is shipped to Iran.
Turkish Energy Minister Taner Yildiz said earlier on Thursday he was not worried about a "clash with the USA" over the trade. "We are talking with the USA," he said.
The new sanctions would allow purchases of natural gas from Iran only if the buyer holds the payment in an account that Iran can draw on to buy goods or services allowed under the law.
But the draft bill would also explicitly ban sales and transfers of precious metals to Iran.
"After giving Turkey this flexibility, Congress will not be sympathetic to a continuation of a 'gold for gas' scheme," said Dubowitz, who has pushed for stronger sanctions on Iran.
Obama issued an executive order at the end of July authorizing sanctions on anyone who helps the Iranian government acquire U.S. dollars or precious metals, including gold.
"We can't comment on any investigations that may be ongoing," an administration official said.