"He submitted his resignation request and is due to leave in mid-July," he said, adding that Ivanov's decision is not politically motivated.
The source said there are no plans to restructure the Security Council, but declined to comment on Ivanov's own plans.
There has been no official comment on Ivanov's resignation, but the Vedomosti daily said he could be named ambassador to a European country, while his replacement could be decided at the July 15 session.
The paper quoted another source as saying Ivanov does not intend to remain in the civil service but join academia, adding, however, that President Putin might not accept his resignation.
The Novye izvestia daily suggested Ivanov could become yet another candidate successor to Putin, whose presidential term expires in 2008.
According to one theory, Ivanov is being groomed for successor by one influential Kremlin grouping: He is loyal, obedient and rather vulnerable, the paper says, since most of his income (an estimated $5-7 million a year) purportedly comes from the gambling business in which has a share.
