A former ally of the president, Sall will take on the 85-year-old Wade in a second round of voting after emerging as the runner-up in last Sunday’s tight election.
He urged failed presidential candidates, opposition movements and singer-turned-political activist Youssou Ndour to back him and “complete the process for a new democratic alternance”.
The run-off will be held on either March 18 or 25, he said.
Provisional results put Wade, 85, in the lead with 34.97 percent and credited Sall with 26.21 percent, a humiliating blow to the incumbent who had promised a crushing first round victory.
ddressing journalists, Sall, 50, praised a transparent election on Sunday and promised wide-ranging reforms if elected.
Sall, 50, is a member of the opposition June 23 Movement (M23) against Wade’s third term candidacy and its members are most likely to rally around the younger candidate.
Another former prime minister, Moustapha Niasse, came in third with 13.24 percent and has already vowed not to support the incumbent.
“The M23 message is that Wade must get out. The fundamental objective is that Wade’s third term mandate does not happen,” M23 co-ordinator Alioune Tine wrote in the Quotidien newspaper.
The media suggested some opposition candidates might choose to gamble on a few more years under the leadership of the ageing Wade which would give them another shot, than a possible 14 years, or two terms, under Sall.
Wade, who won in the first round in 2007 elections with 55 percent, has said he only wants three more years to finish his “grand projects” but this is widely seen as a bid to line up his unpopular son Karim to succeed him.
The younger Wade was at the centre of the storm which saw Sall — himself once tipped as successor — fall from grace after a meteoric rise which took him through several ministerial portfolios.
In 2008, as head of parliament, he was held responsible for Karim being summoned for questioning over the budget of the Islamic Conference organising committee headed by the president’s son.