Kenyan President Daniel arap Moi today called national elections for September, a year earlier than required, after charging nine days ago that there was "a traitor" being groomed by "foreign powers" to take over the presidency.

Moi made his unexpected announcement at a special meeting of the national governing council of the Kenya African National Union, the country's sole political party. As the party leader, Moi will be the only candidate for the presidency, but he indicated that he would use the elections to purge other government officials with whom he has become dissatisfied.

Moi has not said what "foreign powers" he thinks are attempting to groom a replacement for him, but it is commonly known that Britain, Kenya's former colonial ruler and a longtime staunch ally, has fallen into a troubled relationship with the Kenyan government.

At the same time, relations have remained good with Washington, which considers Kenya strategically important as a staging area for the planned U.S. Rapid Deployment Force.

It had been widely assumed before today's meeting that Moi would use the occasion to name the dissident elements within his government. His failure to do so and dispel the climate of suspicion here points toward the likelihood that the issue will remain open throughout the coming election campaign.

"It is absurd that some of the people I have appointed to senior positions have outwardly pretended to be loyal to me, and yet behind the scenes, they have been using their positions to promote their selfish ambitions," Moi said today, without naming names. "I wish therefore to confirm that I stand by what I said at the Kisii rally on May 8 regarding activities of some people who are seeking assistance from their foreign masters to promote their excessive ambitions.

"I am determined to rectify the weaknesses which we have been witnessing in the government because of the conduct of these evil-minded people. In order to clean the system, I have therefore decided that all elected leaders, including myself, will seek a fresh mandate from the electorate."

Although the supposed rival has not been identified, the situation has revealed that there is dissension at high levels and probably among Moi's closet advisers.

The only politician who has publicly attempted to clear his name is Constitutional Affairs Minister Charles Njonjo, who issued a statement yesterday denying he was involved and reiterating his support for Moi.

Njonjo has for many years been a recognized power in Kenya. In his former position as attorney general he was an influential adviser to the late president Jomo Kenyatta and to Moi in the period immediately after Kenyatta's death in 1978. Njonjo resigned his appointive position as attorney general to run successfully for Parliament in 1980.

As a member of the once-powerful Kikuyu tribe, Njonjo often feuded with Mwai Kibaki, Kenya's vice president and also a Kikuyu. After his charge about a "traitor," Moi took a public stand in support of Kibaki in what has been seen as a move to protect Kibaki's name.

Britain's ambassador, Leonard Allinson, no longer has easy access to Moi, who failed to damp speculation as to Britain's role in the affair when he met with Allinson Friday.

Some Kenyans are angry at the welcome Britain has given vocal Kenyan university lecturers who fled to London after an abortive coup attempt by junior Air Force officers last Aug. 1.

Some of Moi's close advisers have also taken exception to what they consider to be Britain's paternalistic attitude in its provision of aid to Kenya. Britain is the country's largest aid donor.

Like Britain, the United States has attempted to support the Kenyan economy while at the same time exercising some influence. After local Firestone and Union Carbide factories were forced to shut down temporarily because of government refusal to allow them to import raw materials, Vice President Bush reportedly tied badly needed additional U.S. aid to better cooperation with American investors during his visit to Kenya last November.

Kenya's economy has been damaged not only by global recession but also by internal misadministration and corruption. The government has a deficit of about $145.5 million that must be met before the coming year's budget is introduced next month.

If new sources of revenue cannot be found, Kenya may be forced to revert to its old system of borrowing heavily from commercial banks--a habit that resulted in the International Monetary Fund suspending its standby facility last year. A new facility was agreed upon in March but could be jeopardized by heavy domestic borrowing.

The World Bank also reportedly has doubts about releasing funds Kenya is counting on. Withdrawal of these two loans would mean serious financial difficulties for Kenya and further undermine Moi's position.