Ambani filed an application before Special CBI Judge O P Saini, saying he had received the summon on July 23 and "owing to extremely short notice of just two days", it would not be possible for him to appear before it.
"I wish to state that owing to the extremely short notice of just over two days and my large number of pre-scheduled and pre-committed business engagements, it will not be possible for me to travel to Delhi on July 26, 2013," he said, adding that he would appear before the court any day after August 15.
"I request your honour to kindly grant an adjournment for my appearance and fix a new date at any time after August 15, 2013 at your convenience," Ambani said.
Earlier, during the day, the Supreme Court had refused to give an urgent hearing on the plea of Reliance Telecom Ltd (RTL) challenging the trial court's order summoning Ambani and his wife Tina Ambani as prosecution witnesses in the 2G case.
The apex court has posted RTL's application for hearing on Monday before a special bench, comprising justices Singhvi and K S Radhakrishnan, which is hearing all the matters pertaining to the 2G scam.
The special court had allowed CBI's plea that the testimony of Anil and Tina Ambani may throw light on alleged investment of over Rs 990 crore by his group companies in Swan Telecom, facing trial in the case along with its promoters Shahid Usman Balwa and Vinod Goenka.
Agreeing to hear his plea, the Supreme Court had on July 23 asked Swamy to inform the JJB about his pending petition in the apex court.
Accordingly, Swamy had informed the JJB about the direction given by the apex court pursuant to which he was asked by the Board to furnish an affidavit in this regard.
Swamy's plea will come up for hearing before the apex court on July 31.
He has in his petition sought that the "mental and intellectual maturity" should be considered instead of age limit of 18 years for such offenders while fixing their culpability and contended that his plea would become infructuous if the JJB went ahead with pronouncement of verdict, which was scheduled for today.