The United States says six weeks has been "quite long enough" for Iran to consider a Western incentives package aimed at defusing a nuclear standoff.
A State Department spokesman Sean McCormack says any government could make a decision in a six-week period that it will engage in talks and meet conditions.
He spoke on the eve of a meeting in Brussels between European Union foreign policy chief Javier Solana and Iran's top nuclear negotiator, Ali Larijani. An EU spokeswoman, Christina Gallach says the bloc wants to hear Iran's response during the meeting.
Solana presented the incentives package to Iranian officials on June sixth.
The package, drawn up by the five permanent U.N. Security Council members (U.S., Britain, France, Russia, China) and Germany, offers incentives if Iran suspends uranium enrichment. There is the possibility of sanctions if Tehran does not.
Iran has said it will not respond until August.
The U.S. and many of its European allies believe Iran is planning to build nuclear weapons. Iran insists its nuclear program is for peaceful purposes.