A senior U.S. diplomatic envoy has extended a visit to Khartoum aimed at persuading the Sudanese government to approve deployment of United Nations peacekeeping forces in Darfur. Assistant Secretary of State for African Affairs Jendayi Frazer is seeking a meeting with Sudan's President Omar al-Bashir to deliver a message from President Bush.

Assistant Secretary Frazer has met with senior Sudanese figures, including Foreign Minister Lam Akol, but has not been granted a meeting with President al-Bashir, on the stated grounds the Sudanese leader has been too busy.

But officials here say the State Department's chief African affairs official is extending her stay in Khartoum, and that they remain hopeful she will be allowed to meet with Mr. al-Bashir to personally deliver the message from President Bush.

The United States has led efforts in the U.N. Security Council on a resolution to upgrade the current African Union peacekeeping mission in Darfur into a full-scale blue-helmeted U.N. peacekeeping force.

The 7,000-member AU mission in Darfur, or AMIS, has been plagued by financial and logistical problems and its mandate expires September 30. Under the U.S. and British-sponsored draft resolution, African troops already in Darfur would become the core of the U.N. force, which would then be enlarged to more than 17,000 troops.

In a talk with reporters, State Department Spokesman Sean McCormack said Assistant Secretary Frazer was being persistent in her pursuit of a meeting with the Sudanese leader, and might scrap plans to attend a conference on Somalia in Stockholm Tuesday in order to fulfill her mission in Khartoum.

McCormack said dealing with the Darfur issue has been difficult, but that the United States will persevere in its drive to upgrade the peacekeeping presence:

"The Sudanese government needs to follow through on what it agreed to do," said Sean McCormack. "If there's a peace agreement in Darfur, then it would allow a blue-helmeted force into Darfur. We would expect that that would happen. And we are also going to be working up in New York on the Security Council resolution that would create that blue-helmeted force, and to have a transition from AMIS to a blue-helmeted force done by October 1.

Sudan signaled acceptance of the force upgrade in May when a Darfur peace accord was signed in Nigeria. But it has since reneged, with President al-Bashir even suggesting Sudan might forcibly resist its introduction.

He has countered with a plan to deploy more than 10,000 Sudanese troops to pacify Darfur, but human rights groups contend that would spark new fighting with Darfur rebels and worsen the region's humanitarian crisis.

In a related development, Spokesman McCormack said Assistant Secretary Frazer raised with the Sudanese foreign minister and other officials the case of American journalist Paul Salopek, who was arrested in Darfur earlier this month along with a Chadian driver and interpreter.

Salopek, a Pulitzer Prize-winning correspondent for the Chicago Tribune, has been accused of espionage, false reporting and entering Sudan illegally.

McCormack said U.S. diplomats have visited Salopek in prison and attended at least two of his court sessions.

He said the United States considers the case a matter of great interest and hopes that any judicial process is fair, speedy and transparent.

Journalism watchdog groups have also spoken out on the case. The Paris-based Reporters Without Borders has called the charges ridiculous and said Salopek was just trying to cover the tragic situation in Sudan.

The Committee to Protect Journalists in New York said it was deeply troubled by the arrest and charges, which it called a grave threat to press freedom, and appealed to Sudanese authorities for the 44-year-old reporter's early release.