By THE NEW YORK TIMES

The United States government said Tuesday that it would withhold tens of millions of dollars in aid to Nicaragua because of the governing Sandinista party’s role in municipal elections that the opposition contends were rigged.

“We had hoped, for the sake of the Nicaraguan people, that the government would continue the country’s trend toward peaceful, democratic and credible elections,” said John J. Danilovich, chief executive of the Millennium Challenge Corporation, the United States government agency that had issued the grants to Nicaragua to fight poverty. “I’m afraid recent evidence shows that this is not the case.”

Nicaragua’s vice minister for international cooperation, Valdrack Jaentschke, called the decision to freeze the estimated $60 million in grants “unacceptable” and “unethical.”

To receive a total of $175 million in grants for farmers and entrepreneur, Nicaragua had to meet various conditions, including a commitment to political freedom, Mr. Danilovich said in a statement.