Deputy Transportation Secretary Michael P. Jackson, who has been mentioned as a possible successor to Secretary Norman Y. Mineta, said July 7 he would resign Aug. 1 and return to the private sector.

Jackson, who basically ran the department while Mineta was out with back problems, said the demands of his high-pressure job had taken too much time from his wife and his 8-year-old daughter.

Jackson, who came to the post from a vice presidency at Lockheed Martin Corp., also said the transportation post was becoming a financial burden for his family.

 “Michael has been an invaluable asset to the department and the Bush administration,” Mineta said in a statement. “Over the past few years as my deputy, he has brought to his position the highest possible combination of strategic insight, practical transportation experience and political acumen.”