U.S. President Barack Obama is calling on Sudan's government to stop its “campaign of intimidation” in the country's southern border area or face international isolation.

Mr. Obama told VOA Tuesday that Sudan's government must immediately cease its military actions in southern Sudan including aerial bombardments and the forced displacement of civilians.

He said if Sudanese leaders fulfill their obligations and choose peace, the United States will take the steps it has promised to normalize the relations between the countries. However, he said if they flout their obligations, they will face pressure and isolation and will be held accountable for their actions.

Mr. Obama said the United States is deeply concerned by the crisis that is unfolding in southern Sudan, including the fighting in Southern Kordofan state and the assaults on innocent civilians.

Northern Sudanese troops have been fighting southern-aligned militia for more than a week in Southern Kordofan state. The United Nations says northern jet fighters dropped 11 bombs on the area Tuesday.

The north's army also last week seized control of the neighboring Abyei region, which also lies on the north-south border.

Both north and south Sudan claim ownership of Abyei. The dispute has raised fears of renewed war in Sudan as the south prepares to declare independence on July 9.

North and south Sudan fought a 21-year civil war that ended with a 2005 peace deal. The south voted overwhelmingly to split from the north in a January referendum.

Abyei was scheduled to hold a separate referendum on whether to join the north or south, but the poll failed to happen because the sides could not agree on who was eligible to vote.