The Prime Minister was originally scheduled to appear later in the year, after the poll.
He has insisted the timing was up to committee chairman, Sir John Chilcot.
Mr Brown will now speak before the election, Sky News understands.
After increasing pressure from political opponents, Mr Brown wrote to Sir John earlier this week to make it clear he would be "happy" to attend at any time.
"I am clear that it is a matter for you how you conduct the Inquiry and that it is, and must remain, entirely independent of Government," the Prime Minister wrote.