The United States expressed concern Tuesday about rising political tensions in Armenia, where government security forces have dealt harshly with protesters calling for the resignation of President Robert Kocharian.

The written statement from State Department spokesman Richard Boucher said the United States is concerned about the political situation in Armenia and particularly the "sharp escalation in confrontation" between the government and opposition.

Mr. Boucher called on both sides to enter into a dialogue that will lessen tension and focus the political process in the country on the challenges of continued political and economic reform.

The U.S. statement came after opposition political leaders in Armenia vowed to press ahead with a campaign to force Mr. Kocharian's resignation following the breakup of an anti-government rally in the capital, Yerevan.

News accounts said police used water cannons and stun grenades to disperse a crowd of about 3,000 demonstrators along the city's main thoroughfare near the parliament. Opposition sources said several protesters were injured, others arrested, and opposition party offices ransacked.

Government officials defended their handling of the incident, saying protesters provoked the police by throwing stones and calling for the violent overthrow of the government. The opposition denies the claims.

In his statement, spokesman Boucher said physical assaults, raids on political party offices, and widespread arrests and detentions of opposition activists by police "do not contribute to an atmosphere conducive to political dialogue."

He said the United States calls on both sides to respect the role of peaceful assembly and to take all steps to prevent violence.

Armenian opposition elements have been staging almost nightly protests in the last week to push demands for the departure of Mr. Kocharian, whom they blame for high poverty rates, an authoritarian governing style. They also accuse him of rigging the March 2003 election in which he gained a second five-year term in office.

The State Department said at the time it concurred with an assessment by the Organization for Security and Cooperation in Europe that the election was marred by serious irregularities and fell short of international standards.

It said the election was deeply disappointing and that the Armenian leadership had missed an important opportunity to advance democracy by holding a "credible" election.