Bashir said the Sudanese government won't allow South Sudan to use its export terminals for oil exports.
South Sudanese oil production and exports halted last year following payment disputes with the Sudanese government. Exports resumed earlier this year after lengthy multilateral negotiations, though Bashir said he was frustrated with southern rebels who may be getting financing from oil revenue.
Jonathan Temin, director of the Sudan and South Sudan program at the United States Institute of Peace, told The New York Times the decision was a step in the wrong direction.
"[Bashir's decision is] a discouraging development given the relative progress over the past couple of months," he said in an interview published Monday.
South Sudan gained independence in 2011 as part of a peace deal with Sudan brokered with the U.S. government's help in 2005.
Both Sudans approached the brink of war over disputed oil territory along their shared border last year.
The Sudanese information minister was quoted by the Times as saying Sunday the oil move wouldn't enter into force immediately.
"You don't shut the oil off like a faucet," he said.
Exploding whale video goes viral on Internet
Martin Bashir resigns from MSNBC over Sarah Palin comments