BRUSSELS — The secretary general of the NATO alliance, Anders Fogh Rasmussen, said on Monday that the wars in the Balkans in the 1990s illustrated what might befall Syria unless Russia and the West agreed on a “unified, clear message” to the Syrian government to stop the violence.

In an interview, Mr. Rasmussen said that alliance members were disappointed by the failure of President Bashar al-Assad’s government to comply with the peace plan promoted by Kofi Annan, the special envoy for the United Nations and the Arab League.

Mr. Rasmussen said he agreed with the British foreign secretary, William Hague, who told Sky News over the weekend that the crisis in Syria was starting to resemble the sectarian warfare in Bosnia two decades ago, another time when Russia and the West were at odds over how to stop the violence.

“I think one part of the lessons learned from the events in the Balkans is the serious consequences it may have if the international community can’t speak with one voice, and can’t reach an agreement on how to address the security challenges,” Mr. Rasmussen said. “That’s exactly what we’re witnessing in Syria.”

He repeatedly emphasized in the interview that NATO had no plan or intention to intervene militarily in Syria, as the alliance eventually did in Bosnia and in Kosovo, and more recently in Libya. A United Nations Security Council resolution would be needed to authorize any NATO military action of that kind, he indicated.

“If we are to facilitate a peaceful solution in Syria,” Mr. Rasmussen said, “I think it’s of utmost importance that the international community stands united and sends a unified, clear message to the Assad regime that it must live up to its international obligations and stop the crackdowns on the civilian population, and accommodate the legitimate aspirations of the Syrian people.”

Mr. Rasmussen expressed concern about recent developments in the Balkans, where NATO is still stationing more than 5,000 troops. Adm. James G. Stavridis, the supreme commander of the alliance’s forces in Europe, wrote in a blog post last week that NATO would maintain that troop level “for the foreseeable future” because “tension continues to be high” in the Balkans, particularly between ethnic Serb and ethnic Albanian communities in northern Kosovo.

Mr. Rasmussen said the alliance postponed plans to reduce the NATO troop presence gradually in the Balkans in part because the European Union’s mission in Kosovo — made up mostly of police and judiciary officials — is being cut by one-quarter this month.

Serbia on Monday inaugurated a new president, Tomislav Nikolic, whose nationalistic statements have raised concerns that he might undo the region’s efforts toward reconciliation. Mr. Nikolic is scheduled to visit Brussels this week to meet with European Union officials, but no stop at the NATO headquarters here is planned.

Serbia officially became a candidate to join the European Union in March. Mr. Rasmussen, a former Danish prime minister, said he trusted that Mr. Nikolic would “stick to that European commitment.” He urged the Serbian government and the ethnic Albanian leadership in Kosovo, a former province of Serbia, to refrain from “unilateral steps that can fuel violence and instability.”

Mr. Rasmussen said he was sure that Greece would remain a strong and “highly valued ally” within NATO even if it dropped out of the euro zone or even the European Union. Still, he said, “from an overall Euro-Atlantic perspective,” it would be best if Greece stayed in the euro zone and the union. (Copyright 2012 The New York Times Company 06/12/12)