A top ally of Congolese President

Term limits in Democratic Republic of Congo's 2006 constitution bar Kabila, who has ruled the central African country since 2001, from running for a third elected term in a presidential poll scheduled for November.

The government, however, has said the election is likely to be pushed back because of budgetary and logistical problems. The country's constitutional court ruled last month that Kabila would remain in office if the vote does not take place on time.

The presidents of neighbouring Congo Republic and Rwanda last year pushed through constitutional changes by referendum to allow them to stand for third terms, but Kabila would likely face considerably more opposition to any such move.

Yet in a speech to thousands of supporters at a rally in the capital Kinshasa to celebrate Kabila's 45th birthday, the secretary-general of his PPRD party, Henri Mova Sakani, said that a constitutional referendum was an option.

"If the people decide to go to a referendum, they are going to do it," he said. "The people of Congo Republic did it. The people of Rwanda did it... Learn to read the signs of the times."

Western powers have repeatedly called on Kabila to organise the presidential election and step down this year, with the United States and Britain threatening sanctions in the absence of concrete progress.

They fear that political instability in Congo, which has never experienced a peaceful transition of power and where millions died in regional wars from 1996-2003, could ripple beyond the country's borders.

Dozens died in protests in January 2015 against a revision to the election law that opponents said was a pretext to keep Kabila in power beyond this year. The United Nations and rights groups say the government has since arrested dozens of its critics on trumped-up charges.

READ: Top Congo court says Kabila stays in power if election not held

Kabila has declined to comment publicly on his future plans. Meanwhile, his allies have adopted an increasingly intransigent tone toward foreign critics, with Mova telling advocates of sanctions at a rally last month: "you won't scare us."