Sheikh Salman vowed not to "mortgage" the crisis-torn world football body's future to win votes in his battle with four rivals led by Gianni Infantino, the UEFA general secretary.
The Confederation of African Football (CAF) and Asian Football Confederation (AFC) leadership reaffirmed their support for the Bahrain royal at meetings in Zurich ahead of Friday's vote.
The two federations have 100 votes of the 209 at FIFA.
CAF first vice president Suketu Patel said: "We discussed our concerns and who we think can deliver and we supported him (Sheikh Salman), we think he would be the person to care about our concerns."
Patel said that even if not all of the 53 African votes go to the sheikh, the vast majority will. "I think it will be a bloc, that is the key, 53 or 50 it doesn't matter."
Other candidates -- particularly Infantino and Prince Ali bin al Hussein of Jordan -- are certain they have persuaded African federations to vote for them however.
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Because of divisions within the 47-member AFC, rivals also believe they have some Asian votes. Prince Ali is certain to get his native Jordan while Iraq and Palestine have said they will back him.
But Sheikh Salman got "united" support at a special AFC meeting, a statement released by the confederation said. Sheikh Salman has been the AFC president since 2013.
AFC vice president Praful Patel, head of the All India Football Federation, said: "Sheikh Salman is a proven leader as he has demonstrated at the AFC. At this time FIFA needs someone to lead and be a strong president."
The election campaign has been marked by vows to substantially increase the amount of money that FIFA gives back to national federations.
But the sheikh has said some of the promises risk bankrupting the world body, which has spent heavily since corruption scandals erupted last May and forced its longtime president Sepp Blatter to leave.
"I can promise you that I will not compromise the principles that have helped restore stability and unity to Asian football," the sheikh said at the Asian meeting.
"This is not a time to mortgage FIFA's future for a few votes. This is a time, as the acting FIFA president (Issa Hayatou) wrote to you this week, to set our great game back on the path to regaining credibility and confidence of all our stakeholders. We need to redefine, restructure and revitalise FIFA."
Jerome Champagne, a former FIFA official from France, and Tokyo Sexwale, a South African businessman and politician are also in the FIFA vote on Friday.