New Delhi, June 1 : Congress leader Rahul Gandhi, who has been summoned by the Enforcement Directorate (ED) in connection with the National Herald case, has requested the probe agency to give him some more time to join the investigation. The ED has summoned both Sonia Gandhi and Rahul Gandhi to join the probe. Sonia Gandhi has been summoned on June 8 whereas Rahul Gandhi has been summoned on Thursday (June 2). Soon after receiving the summon, Rahul Gandhi wrote to the ED saying he won't be able to join the probe tomorrow (Thursday). However, no such request has been made by Sonia Gandhi and she is expected to join the probe on the given date. ED wants both of them to appear before the probe agency to record their statements. The sources have said that both have been asked to appear before ED's Delhi headquarters. The case has been lodged against various Congress leaders including Gandhis for allegedly misappropriating National Herald fund. Initially the case was lodged with the Central Bureau of Investigation (CBI) and ED case is based on the CBI's case. /IANS