The FIFA president said British newspaper The Sunday Times has agreed to bring its source to meet senior FIFA officials, who will decide whether to order a new investigation into alleged World Cup bidding corruption.
"(The Sunday Times) are happy, they agreed that they will bring this whistleblower here to Zurich and then we will have a discussion, an investigation of this," Blatter said.
The whistleblower claims that FIFA executive committee members Issa Hayatou and Jacques Anouma were paid $1.5 million to vote for Qatar. The emirate's bid beat the United States in a final round of voting last December.
Blatter did not rule out reopening the 2022 vote if corruption could be proved, but urged taking the matter "step by step."
"It's an alarming (idea) but don't ask me now if yes or no," he said.
The FIFA president said his organization is "anxiously awaiting" more evidence before asking its ethics committee to examine allegations made in Britain's parliament last week.
"It is of paramount importance that we have this situation clarified on (May) 27th," said the 75-year-old Blatter, who stands for re-election against Qatari challenger Mohamed bin Hammam five days later.
Bin Hammam played a central role in Qatar's victory to secure 2022 World Cup hosting rights.
Qatar's success has been called into question since The Sunday Times submitted claims to a British lawmakers' inquiry into soccer governance, which included England's failed bid to win 2018 hosting rights.
Lawmakers released claims by a former bid employee that Qatar agreed to pay members of FIFA's 24-man executive committee for their votes.
Hayatou, who is from Cameroon, leads the Confederation of African Football and is a FIFA vice president. Anouma is president of Ivory Coast's football federation.
The whistleblower said Qatar agreed to pay a third African voter, Amos Adamu, for his support. The Nigerian was later suspended from voting after a FIFA ethics court ruled he solicited bribes from undercover Sunday Times reporters posing as lobbyists.
Blatter said the newspaper and its whistleblower would meet with FIFA secretary general Jerome Valcke and legal director Marco Villiger.
FIFA's independent ethics committee could be summoned within days to hold its own probe.
"The ethics committee is already alerted and alarmed. They are not just lying on the beach," Blatter said. "All the members will come for the Congress (on June 1) so it will be easy to have an ethics committee convened in very short notice."
Blatter said he would play no part in ordering an investigation that could tarnish the reputation of his election opponent.
"What they do is not a matter for the FIFA president," he said.
FIFA is also awaiting evidence to support further allegations made to parliament by David Triesman, the former head of England's bid and the English Football Association.
Triesman told the lawmakers that four long-standing FIFA executive committee members — Jack Warner, Nicolas Leoz, Ricardo Teixeira and Worawi Makudi — engaged in "improper and unethical" conduct in the 2018 bidding, which was won by Russia.
All six FIFA voters have denied wrongdoing.