The U.S. and the European Union said Tuesday they'll press on with sanctions against Iran, even as they hope the promise of new negotiations could lead to a diplomatic solution ending the nuclear standoff.

Appearing together at a news conference in the Bosnian capital of Sarajevo before continuing a joint tour of the Balkans in Serbia and Kosovo, U.S. Secretary of State Hillary Rodham Clinton and EU foreign policy chief Catherine Ashton said both diplomacy and pressure would continue until Iran makes significant concessions over its disputed uranium enrichment activity.

"We continue to try and find ways to move forward on our negotiations," Ashton told reporters in Sarajevo. She cited contact over the weekend between a top aide and an assistant to Iran's chief nuclear negotiator Saeed Jalili, and said she would be reaching out to Jalili "in the near future."

Still, there appeared to be no significant advance in the process since world powers instructed Ashton last month in New York to speak with Jalili and gauge Iran's seriousness on coming into compliance with its international nuclear negotiations. The West fears Iran may be trying to develop nuclear weapons, a charge Tehran denies.

The West has demanded that Iran must stop enriching uranium to 20 percent purity, shut down its underground Fordo enrichment site and ship its 20 percent stockpile out of the country. In return, Iran has been offered civilian plane spare parts and 20 percent-enriched nuclear fuel for its medical research reactor in Tehran.

Clinton said the U.S. message to Iran is clear. "The window remains open to resolve the international community's concerns about your nuclear program diplomatically and to relieve your isolation, but that window cannot remain open indefinitely. Therefore, we hope that there can be serious good-faith negotiations commenced soon."

Iran has sent mixed signals on its nuclear program. World powers cited increased flexibility from Iran in September when they agreed to lay the groundwork for a new round of negotiations, and on Tuesday Iran's Foreign Ministry said the standoff could be resolved if the U.S. and its partners recognize Iran's right to produce nuclear fuel.

But senior Iranian officials also have threatened to boost enrichment levels if the West doesn't ease sanctions. And the U.S. and its partners say measures that are crippling the Iranian economy will remain in force until Tehran first starts coming into compliance with its international obligations.

Clinton and Ashton spoke during the first leg of their tour of the Balkans, where they are urging rivals ethnic groups and governments to settle their differences for the good of their nations.

Seventeen years after the U.S.-led intervention ended Bosnia's civil war, Bosnia's Muslims, Serbs and Croats are split on how to unify the country or even to dissolve their federation entirely into separate ethnic parts. The Serb republic and the Bosniak-Croat federation have their own governments and parliaments, held together only weakly by a three-member presidency that Clinton and Ashton met with.

Clinton called efforts by some to roll back the Dayton Accords passed during the presidency of her husband "totally unacceptable," a reference to Bosnian Serb leader Milorad Dodik's call for the dissolution of Bosnia. He has also denied the genocide of Bosnia's Muslims in the 1990s.

Clinton urged all Bosnia's leaders to "put aside their political differences, put aside the rhetoric of dissolution, secession and denial of what tragically happened in the war." She and Ashton said the country's slow pace of reforms and the inability of leaders to look past their ethnic constituencies are holding back its hopes of joining the EU and NATO, and leaving it behind neighbors such as Serbia, Croatia and Kosovo.

Later in Belgrade, the two met Serbia's nationalist president, Tomislav Nikolic, and Prime Minister Ivica Dacic.

Clinton told them that normalizing ties with Kosovo, which broke off from Serbia four years ago, is critical for Serbian aspirations of entering the 27-nation European Union. She urged progress in talks with Kosovo about issues such as freedom of movement, customs, utilities and government services, without calling for Belgrade to immediately recognize the independence of its former province.

After Serbia, the pair flew together on Clinton's plane to Kosovo's capital of Pristina, where they'll press top officials on similar matters on Wednesday. Afterward, Ashton will drop off the trip and Clinton will travel on to Croatia and Albania, NATO's two newest members.


Associated Press writers Aida Cerkez in Sarajevo and Jovana Gec in Belgrade contributed to this report.