Iran's top atomic nuclear negotiator, Ali Larijani, said that the Islamic republic was "serious" about defusing the standoff but made it clear that little could be expected straightaway.
With the threat of UN sanctions hanging over it, Iran is facing mounting international pressure to respond by the end of the month to a package of incentives.
But Tehran refuses to suspend uranium enrichment activities, a key condition of the offer.
A senior Iranian official made it clear in Brussels that no response can be expected next week and Iranian President Mahmoud Ahmadinejad has said that Tehran will give its formal response to the offer in August.
The United States has increased pressure on the government in Tehran by repeating the sanctions threat.
The renewed pressure comes ahead a meeting of leaders of the Group of Eight major industrial powers in Saint Petersburg on July 15.