The United States says it is concerned at the inability of both the government of the Democratic Republic of Congo and an opposition coalition to implement a political transition agreement they reached in December after months of unrest.
The State Department faulted both sides for failing to make the necessary compromises to carry out the agreed-upon steps, which include the appointment of a prime minister.
"Failure to move ahead with the accord clearly thwarts the will of the Congolese people and jeopardizes the progress achieved thus far," acting spokesman Mark Toner said in a statement.
President Joseph Kabila was due to leave office December 19 at the end of his second term, but elections to choose his successor were postponed and Kabila has remained in office.
The agreement between the government and the opposition was supposed to set up a transitional authority led by a prime minister until new elections could be held late this year.
But the two sides remained split on how to implement the agreement, and the country's largest opposition party has called for a large protest on April 10.