Sudan has threatened to close its border with South Sudan and cut off food aid unless South Sudan expels rebels who are allegedly taking refuge in its territory.

Sudan's president Omar Al Bashir had been due in Juba over the weekend. That trip was called off at the last minute. Instead Sudan's foreign ministry has issued a short, sharp statement. State Minister Kamal Ismail says, quote, 'Juba must clearly make its political decision on expelling the movements.'

It's not the first time Khartoum has made this demand. Khartoum routinely accuses the south of harbouring rebels - which the south routinely denies. But Bashir's government is citing an undertaking given by Juba just last month. South Sudan's First Vice-President Taban Deng was here - and Khartoum says he'd promised the expulsion within 21 days. That deadline is now passed.

The border was only reopened in January, after five years. Its closure damaged the economies of both countries. And neither Sudan nor the south can afford another long-term shutdown.