Secretary of State Hillary Rodham Clinton delivered a blunt warning to squabbling Balkan leaders Tuesday that they risk being left behind as their neighbors join economically and diplomatically with Europe.

Standing next to Bosnia’s three presidents — one apiece representing ethnic Bosniaks, Croats and Serbs — Clinton was most critical of positions taken by the Serbs.

“It is totally unacceptable that 17 years after the war ended, some still question Bosnia-Herzegovina’s sovereignty and territorial integrity,” Clinton said.

That was a reference to Bosnian Serb nationalist threats to dissolve the country, which was formed as the result of a U.S.-brokered peace plan.

“Such talk is a distraction from the problems facing the country and serves only to undermine the goal of European integration,” Clinton said. “The Dayton accords must be respected and preserved, period.”

Bosnian leader Bakir Izetbegovic agreed, telling Clinton after a lengthy meeting that it is past time to discard “wasted” ethnic agendas. “The future is on us,” he said.

Clinton also commented on the results of Sunday’s parliamentary election in Ukraine, in which the ruling party appears to have held on to power in balloting strongly criticized by international observers.

The election was “a step backward for Ukrainian democracy,” she said. “We reiterate our deep concern at the politically motivated convictions of opposition leaders, including former prime minister [Yulia] Tymoshenko, that prevented them from running and standing in these elections.”

Clinton began a five-nation Balkans tour in this bullet-pocked city, where tiny graveyards tucked into roadway medians and on mountainsides above her hotel are a reminder of the three-year civil war that killed an estimated 100,000 people in the 1990s.

Clinton is tending to what a senior aide called “unfinished business” in the Balkans two decades after the start of ethnic wars among members of the former Yugoslavia.

The siege of Sarajevo and the massacre of Muslims in Srebrenica led Clinton’s husband, then-President Bill Clinton, to expand the U.S. involvement in what became the largest overseas engagement of his presidency.

Bosnia and Kosovo represent the largest pieces of unfinished business. Clinton, joined by the European Union’s foreign policy envoy, saw each of the ethnic leaders in Bosnia-Herzegovina, which is legally unified but is run as two semi-independent and often-fractious entities.

Unifying the country and reforming economic and political structures built on ethnic fault lines is essential to achieving Bosnia’s stated goal of joining the European Union.

“We have not been shy about saying and being clear that we’re disappointed that the leaders of Bosnia and Herzegovina have not put the interests of the country first oftentimes and instead have promoted narrow ethnic or party or personal agendas,” a senior State Department official said ahead of Clinton’s trip.

The official spoke on the condition of anonymity to preview Clinton’s closed-door meetings with Bosnia-Herzegovina’s presidents.

Clinton and E.U. High Representative Catherine Ashton were reinforcing a message that the leaders have largely ignored: to reform long-standing problems of too much state property ownership and too little authority for the central government.

The ethnic rift in Bosnia appears no better 17 years after the end of the war in 1995, and the country is faring worse than many neighbors economically.

Bosnian Serbs reject any strengthening of central institutions, which is sought by Muslims and the country’s international backers, and Serb leaders warn that their entity could break away and negotiate separately on E.U. entry.

Opinion polls in Bosnia have repeatedly shown majority support for membership in the European Union, whose economic benefits remain attractive despite the bloc’s current fiscal woes. Bosnia is the only Balkan country yet to seek E.U. membership, which it may do by the end of this year. Serbia’s E.U. bid was helped by internal reforms and the arrest of war-crimes suspects.

The ongoing political rivalries and ethnic one-upmanship in the Balkans are mostly nonviolent, but the recent past of civil war and genocide feels close to the surface. The U.S. and European focus on these old problems comes as the world watches civil war unfold in Syria. The United States and NATO oppose a no-fly zone and air campaign in Syria of the kind imposed in the Balkans, although that could change.

Clinton and Ashton traveled together from Bosnia to Serbia and Kosovo, countries also born of the Bosnian war. Clinton will also visit Croatia and Albania this week.

Serbia rejects Kosovo’s unilateral declaration of independence in 2008. The United States and about 90 other nations recognize Kosovo as independent. Although 22 of the European Union’s 27 members have recognized Kosovo, the body as a whole has not.

Kosovo’s minority ethnic Serbs also oppose its separation from Serbia and its leadership by ethnic Albanians in the capital, Pristina.

Clinton made a point of scheduling a meeting Wednesday with ethnic Serb “returnees” who had earlier fled or been pushed out by the Albanian majority.

Talks between Serbia and Kosovo, launched in March 2011 under E.U. auspices, were suspended before May elections in Serbia, won by nationalists. Last week, however, the prime ministers of Serbia and Kosovo met with Ashton in what the European Union hopes will become a new phase of talks.

In Belgrade, Clinton told Serb leaders that they should abide by existing agreements with Kosovo and move forward with political talks.

“This dialogue does not require Serbia to recognize Kosovo. We understand the constitutional and political difficulty of that occurring,” Clinton said. But it does require hard work on less politically fraught issues that can improve daily life for Serbs and Kosovars, she said.

The two governments have made some progress in customs cooperation, land records and recognition of education diplomas, leaving tough negotiations for later.

“We are not going to recognize Kosovo, but we are ready to talk,” Serb Prime Minister Ivica Dacic said after meeting Ashton and Clinton.