The United States on Tuesday threatened sanctions against the Democratic Republic of Congo if elections are not held this year and urged the UN Security Council to punish those responsible for a flareup of violence.
Under a deal reached last year and backed by the Security Council, President Joseph Kabila was allowed to remain in office beyond his term until elections in late 2017.
But concerns are growing that the deal is collapsing after the head of the electoral commission said last week that the vote will likely not be held this year.
"Election delays cannot continue," US Deputy Ambassador Michele Sison told the council during a meeting on the crisis in the mineral-rich African country.
"The international community must step up and apply more pressure, not only on President Kabila and his government but also on the independent national electoral commission," said Sison.
The deputy ambassador demanded that the commission "immediately" publish an electoral calendar and specifically set a date for the presidential election to put in motion the DR Congo's first democratic transition.
The United States and the European Union have imposed sanctions on several officials close to Kabila over the election delays and human rights abuses, in particular in the Kasai region.
"We are ready to take additional action to sanction those who stand in the way of the DRC's first democratic transition of power," said Sison.
"The Security Council should also consider targeted sanctions to reduce the violence in the DRC and help pressure all stakeholders to play a more constructive role in moving the country forward," she added.
France and Britain also demanded that a date for the presidential vote be announced and stressed that there was no alternative to the New Year's Eve agreement on ending the political crisis.
UN peacekeeping chief Jean-Pierre Lacroix told the council that worsening violence had led to a sharp increase of 26 percent in the number of displaced people over the past two months to reach 1.3 million.
Lacroix cited "disturbing reports of summary executions and rapes including of civilians by the security forces" and that "dozens of mass graves" have been reportedly uncovered in Kasai province.
A UN commission of inquiry has been established to investigate the killings in the Kasai while a separate UN panel is preparing to release this month the findings of its probe of the murder of two UN experts.
The bodies of American Michael Sharp and Swedish-Chilean Zaid Catalan were found in March, weeks after they had disappeared while investigating reports of mass graves in the Kasai.