Adm. Bobby Ray Inman plans to stay on in his post as deputy director of the Central Intelligence Agency until Labor Day, if necessary, until his successor is confirmed by the Senate.
President Reagan expressed ''deep regret'' at the four-star admiral's decision announced Wednesday to resign from the CIA and the Navy.
In his resignation letter Admiral Inman wrote that he felt he had met the ''initial challenge'' of helping rebuild the US intelligence-gathering apparatus and wanted to ''move on to fresh challenges.'' He told the Washington Post part of the reason for his decision was to increase his income to educate his two sons, aged 16 and 19.
An intelligence source said Admiral Inman had ''never really enjoyed being No. 2 at the agency,'' and there were reports of friction between him and Central Intelligence Director William Casey. Administration sources quoted by the Post said one point of contention was the extent of CIA spying in the United States.
Admiral Inman was seen as a moderating voice in the agency, and was widely respected in Congress. Rep. Edward P. Boland (D) of Massachusetts, chairman of the House Intelligence Committee, called him ''the nation's finest intelligence officer.''