Gates "thinks this is a matter of weeks, not months," Pentagon spokesman Geoff Morrell told reporters as the defence secretary prepared to leave Paris following a meeting with French President Nicolas Sarkozy.
"He thinks that we need it and that we can do it in that time," Morrell added. "In all his meetings he discussed this sense of urgency."
Sarkozy and Gates on Monday agreed to push for "strong" new UN anti-nuclear sanctions against Iran after Tehran announced it would step up its uranium enrichment, a French presidential official said.
Iran said on Tuesday it has started the process of producing 20 percent enriched uranium, defying world powers who have warned of new sanctions unless the Islamic republic halts its sensitive nuclear drive.
Western powers fear Iran is seeking to build nuclear weapons. Tehran insists it wants nuclear power for civilian purposes.
Gates told the Fox news channel on Monday night: "I think it's going to take some period of time, I would say weeks, not months, to see if we can't get another UN security council resolution.
"Then it provides a legal platform for the EU and individual countries to perhaps take even more far-reaching steps."
The UN Security Council has already passed three sanctions resolutions against Iran. France holds the presidency of the council this month, opening a potential window of opportunity to push through a resolution.
