The Democratic Republic of Congo said on Monday it would refuse international financing for a long-delayed presidential election and fund the poll itself, saying donors' conditions amounted to "foreign interference".

The United States and European countries have expressed concern about the electoral commission's plans to use 100 000 new electronic voting machines, saying the system is untested and could allow fraud.

US ambassador to the United Nations Nikki Haley warned Congolese authorities last month to use paper ballots or lose American support for the polls.

Only a fraction of expected international contributions have been disbursed as donors await clarification from authorities about how the vote will be conducted, including whether the commission will follow through on the plans to use the machines.

Government spokesperson Lambert Mende said on Monday the donors' conditions amounted to meddling in Congo's sovereign affairs and urged them to direct their contributions to other sectors such as healthcare and education.

"No country in the world accepts foreign interference in a process that is an exercise of sovereignty," Mende told Reuters.

The presidential election - now scheduled for December 23 - has been repeatedly delayed since Joseph Kabila refused to step down at the end of his mandate in 2016, with the government citing financial constraints as a main reason.

Uncertainty about Kabila's future, including whether he plans to change the constitution to remove term limits that bar him from standing for a third elected term, have sparked violent street demonstrations in which dozens of people have died.

The United Nations has asked international donors to contribute $123-million to support presidential, legislative and local elections over the next two years, whose total cost is expected to run to more than $1-billion.

Mende said the government's decision to reject such aid was prompted in part by an upturn in government revenues from its mining sector, which has left more money to finance the polls.

Congo is the world's biggest source of cobalt and Africa's top copper producer. Mining sector revenue rose nearly 36 percent last year and oil and gas sector revenue doubled.

Election commission president Corneille Nangaa told Reuters on Monday he was aware of the government's decision but had no further comment.