Rwanda's president on Thursday voiced renewed frustration over what he complained was long-term inaction over Rwandan Hutu rebels in the Democratic Republic of Congo.

President Paul Kagame said even though the Democratic Forces for the Liberation of Rwanda (FDLR) had missed a deadline to disarm and were now facing an offensive by the United Nations mission in the DR Congo, Monusco, he was far from optimistic about the prospect of decisive action.

READ: UN troops prepare offensive against FDLR

The FDLR is estimated to include between 1,500 and 2,000 ethnic Hutu fighters, some of whom are accused of having participated in the 1994 Rwandan genocide which left close to a million people dead, mainly ethnic Tutsis.

Opposed to President Kagame's Tutsi-dominated government, they have been based across the border in eastern DR Congo since the genocide, and are accused of staging brutal attacks on civilians, including rapes and murders, and smuggling gold and charcoal.

Kagame told a news conference he was not confident "that things are going to work out the way they should."

"We've been with the FDLR for decades ... and what has been playing out relating to the FDLR has not been helpful at all," he said.

He accused regional players of making "all kinds of excuses when it comes to (dealing with the) FDLR," including saying there are children and civilians among them.

"When it comes to the FDLR, it's like, you know, let's wait," he said.

Monusco head Martin Kobler said last week the UN and DR Congo forces were prepared for a confrontation with the rebels after they missed a January 2 deadline to turn themselves in. Last week DR Congo's government also said the forced disarmament of the FDLR was now "the only option".

READ: UN forces ready to attack FDLR, as Luanda summit is called off