The number two Democrat in the Senate, Dick Durbin, said the US Congress would wait for the results of October 1 talks between the Islamic republic and six world powers over its nuclear program, according to AFP.
"I don't think a matter of days will make a difference. And if diplomacy can work, and move us in the right direction, I'd like to give it a chance," said the Illinois lawmaker, who has sharply criticized Iran's nuclear drive.
Some of President Barack Obama's Republican foes have pushed for action now on legislation that targets Iran's reliance on imports to satisfy its people's consumption of gasoline and other refined petroleum products.
Iran gets most of its gasoline imports from the Swiss firm Vitol, the Swiss/Dutch firm Trafigura, France's Total, the Swiss firm Glencore and British Petroleum, as well as the Indian company Reliance.
Sanctions targeting firms that do energy business with Iran "would certainly give the president more leverage with Iran," said Republican Senator Saxby Chambliss.
But Democrats and some Republicans have rejected that approach, saying they prefer to wait until after the UN General Assembly, the Group of 20 meeting of major economies, and the October 1 discussions.
"It seems to me that the timetable is the appropriate one. If all of this fails, then we will have to take some actions," said the top Republican on the Senate Foreign Relations Committee, Richard Lugar.
"We ought to approach this one week at a time. This is the week for the United Nations and for the United States to engage with European countries and with others who will be instrumental partners -- once again with Russia -- to test out where they are," said Lugar.
"Our current efforts to stop Iran from developing nuclear programs have failed: They're pushing ahead with all speed. They'll continue to do that until we give them some reason not to," said Independent Senator Joe Lieberman.