(CNN) -- The United States is slamming the Sudanese president's assertion that his government would not recognize the new state of South Sudan if it claims the disputed oil-rich region of Abyei.
South Sudan voted to split from the north and is scheduled to declare its independence in July.
In a speech broadcast on state television Wednesday, President Omar al-Bashir said the disputed region of Abyei belongs to the north.
"Abyei is a part of the north and will remain a part of the north," he said, according to the Sudan News Agency.
A top U.S. envoy criticized the remarks.
"Those comments are not helpful at all, and they only serve to inflame and heighten tensions," said Johnnie Carson, the assistant secretary of state for African affairs.
"It is important that both sides ... focus intensely on trying to resolve the key issues that have not been completed under the CPA. Abyei is one of them."
The CPA refers to a comprehensive peace agreement reached in 2005 that allowed South Sudan to vote in a referendum on whether to split from the north. The referendum was part of an agreement that ended two decades of violence between the north and oil-rich south. The unrest led to the deaths of 2 million people, many from starvation.
South Sudan voters overwhelmingly approved the split in January. Al-Bashir has said he will honor the results, though analysts are concerned he might not keep his word.
During his news conference with reporters Thursday, Carson urged al-Bashir and President of South Sudan Salva Kiir to meet and resolve outstanding issues before July.
Journalist Isma'il Kushkush contributed to this report.