GENEVA, Switzerland (CNN) -- Iran's top nuclear negotiator called talks Saturday with European Union foreign policy chief Javier Solana "constructive" but didn't say whether Iran would accept a short-term proposal to jump-start negotiations on the nuclear issue.
Solana, appearing with Saeed Jalili at a news conference, said he expects to receive an answer from Iran in two weeks.
"We still didn't get the answer we are looking for," Solana said, adding that Iranians are being given an opportunity "to interact with the international community."
As a way of addressing concerns that Iran is intent on developing nuclear weapons, EU officials and the United States, Russia and China have proposed that Iran take a six-week break from manufacturing centrifuges that enrich uranium.
Under the proposal, Iran would be allowed to continue to use the more than 3,000 centrifuges it already has but could not make more. In exchange, the five permanent members of the U.N. Security Council plus Germany would not impose further sanctions against Iran during that period.
Iran says it is pursuing nuclear power only for energy purposes.
Jalili indicated that Iran wants to continue talks but gave no indication that the nuclear issue would be resolved soon.
"The experiences we have had in the past years tell us that, alone, different parties cannot resolve this," he said.
Without elaborating, Jalili said Iran has offered a package of proposals, "which is designed to address our common concerns, common worries. In return, we aren't asking for anything."
He said he spoke Saturday morning with representatives from the five Security Council members and Germany.
"I told them that there is a choice which you need to make: 'You are free to work as seven minus one or six plus one,' " Jalili said.
The State Department warned that Iran will face further "disincentives" if it chooses not to cooperate on the nuclear issue.
"We hope the Iranian people understand that their leaders need to make a choice between cooperation, which would bring benefits to all, and confrontation, which can only led to further isolation," department spokesman Sean McCormack said in a written statement.
"The P5+1 made clear to the Iranians that our proposal was serious, and an opportunity for them to engage with the international community on our concerns."
According to McCormack, U.S. Undersecretary of State William Burns delivered the following message during the talks: "The United States is serious in its support for the package Mr. Solana conveyed in Tehran last month, the United States is serious in its support of P5+1 unity, and the United States with its P5+1 partners are serious that Iran must suspend uranium enrichment to have negotiations involving the United States."
The decision to send Burns is meant to send a strong signal but does not indicate a change of the U.S. position on Iran, McCormack said.
Until now, President Bush and Secretary of State Condoleezza Rice insisted that the United States would talk to Iran only after Tehran halted its nuclear program.
There has been somewhat of a thaw in U.S.-Iranian relations in recent weeks. Foreign Minister Manouchehr Mottaki said this month his country was interested in academic and scientific exchanges with the United States.
Mottaki said Iran has proposed resuming flights between Tehran and the United States, and there has been a suggestion that U.S. diplomats be posted in Tehran.
The United States broke off diplomatic ties with Iran in April 1980, after Americans were taken hostage the year before at the U.S. Embassy in Tehran following the U.S.-backed shah.