World powers meeting at the U.N. General Assembly and the G-20 gathering later this month are unlikely to push immediately for tougher sanctions on Iran, an official familiar with preparations for the meetings said on Thursday.

The United States, Russia, France, Britain, China and Germany are evaluating a package of proposals submitted by Iran on Wednesday after giving the Islamic Republic until this month to respond to their demand for talks on its nuclear program.

The Iranian proposals include a global system to eliminate nuclear weapons as well as cooperation on Afghanistan and fighting terrorism. But, crucially, Iran said it would not discuss its uranium enrichment program, which some Western powers fear could be used to build a nuclear bomb.

An official familiar with the deliberations of the six major powers said Iran’s proposals at first glance did not appear to pass “the smell test”. But they were now being digested and analyzed to determine whether they represented an opening for negotiations.

“Depending on how Iran’s recent proposals for talks play out, leaders will be in a position to take stock and decide on what measures might be appropriate as a next step,” a U.S. official said.

Russia, one of the five veto-wielding members of the United Nations Security Council, has already said that the proposals are a starting point and has ruled out imposing oil sanctions on Iran, a step being considered by the U.S. Congress.

The official familiar with the world power discussions said sanctions could not be considered “until everybody is on board. We are not looking for half measures.”

He said the U.N. General Assembly and the G-20 gathering of rich and developing nations in the week of Sept 21 in Pittsburgh were an opportunity for the world powers to take stock on the Iranian nuclear stand-off.

“I doubt there will be a decision to take action at the moment,” he said. “There will be in all likelihood some decision on what should happen next.”

While the world powers had not yet agreed on a course of action, one scenario was for them to issue a statement that would set out certain conditions that Iran would have to meet or face the threat of tougher action, the official said.