A top U.N. official on Wednesday criticized Sudan for undermining an agreement on humanitarian access by expelling the country director of the large aid organization CARE from Darfur.

U.N. Undersecretary-General John Holmes, the humanitarian coordinator, said that the expulsion "clearly undermined both the letter and the spirit" of a joint communique he signed earlier this year with the Khartoum government on facilitating humanitarian activities in Darfur.

Shortly before U.N. Secretary-General Ban Ki-moon upcoming visit to Sudan, the Sudanese government expelled three prominent foreigners -- Paul Barker of the U.S.-based CARE aid organization and diplomats from Canada and the European Union.

In response, Canada's Foreign Affairs Minister Maxime Bernier announced on Wednesday he would expel a diplomat from the Embassy of Sudan in Ottawa on Sept. 1. He said the expulsion of Canada's charge d'affaires in Khartoum was "entirely unjustified."

Holmes, in a statement, said that the joint communique had "relieved many bureaucratic impediments to our work, for which we are grateful.

"However, issues such as those now faced by CARE are a disturbing example of how far we still have to go," Holmes said. "Enabling Mr. Barker to resume his important work would send a positive signal to the international community that the Government of Sudan wishes to further strengthen its partnership with humanitarian actors."

Bakheit Yousef, Sudan's deputy commissioner of the Humanitarian Aid Commission, said on Monday that Barker's expulsion was not connected to his aid work.

"He was doing something related to intelligence or state security, not his humanitarian work. That was the main reason he has been ordered to leave," he said, adding CARE could send a replacement.

AID officials, who spoke on condition of anonymity because of the delicacy of the situation, said that Khartoum had in the past refused to renew visas of experienced relief staff at a time of growing tension between humanitarian groups and Sudan.

Barker, 53, a native of Oregon, denied he had been carrying out any inappropriate work and said he was hopeful the government would hear his appeal.

He said the only explanation he could think of was that the government was unhappy with an internal e-mail he had written to CARE staff in October and which was leaked to the Sudanese press earlier this year.

"It was an e-mail about the security of CARE staff, setting out various scenarios for what might happen in (the western region of) Darfur," he said,

Barker said CARE had spent more than $184 million on aid projects in Sudan since it arrived in the country in 1979. It has spent more than $60 million in the last three years, he added, mostly in the troubled Darfur region.

Asked about the expulsions at a press conference on Tuesday, Ban said he would raise the issue with Sudanese President Omar Hassan Bashir when he meets him next week.

"I'm going to reiterate the strong commitment of the United Nations to help those people, to help those who need our support," Ban said. "In that regard, the Sudanese government should fully implement and fully cooperate with those international communities."

The secretary-general plans to travel to Khartoum, Darfur as well as to Chad and Libya.