Hours after members of the European Parliament urged FIFA president Sepp Blatter to step down immediately, world football's governing body announced initial plans to elect his replacement.
FIFA's executive committee will meet on July 20 in Zurich to decide when -- sometime between December and February -- the election to decide Blatter's successor should be held.
Earlier, lawmakers from 28 European nations meeting in Strasbourg, France, voted on a resolution calling for Blatter to speed up his announced resignation and let FIFA appoint an interim leader.
"FIFA is perplexed by the European Parliament's resolution," said the Zurich-based soccer body which is not obliged to heed the parliament and previously dismissed criticism by lawmaker groups, including the Council of Europe.
Blatter is a target of the American investigation of corruption in soccer, and Swiss prosecutors are leading a separate probe into the 2018 and 2022 World Cup bidding contests.
If Blatter left before the election, FIFA rules require senior vice president Issa Hayatou of Cameroon to step up as interim president.
Hayatou was reprimanded in 2011 by the International Olympic Committee for taking cash payments in the 1990s from FIFA's then-World Cup marketing agency. He also steered through two changes of CAF presidential election rules in the past two years to protect his position.
Hayatou is among 10 past and current FIFA executive committee members who Swiss authorities want to question in their probe of possible financial wrongdoing in World Cup bidding contests won by Russia and Qatar, respectively.
Still, Blatter praised FIFA's handling of the ongoing corruption crisis in the organisation's in-house magazine.
"FIFA is going through difficult times," Blatter said in an excerpt of his column released on Thursday. "This makes me all the more proud that our organization runs smoothly in a crisis."
Blatter appeared to be referring to the smooth-running Under-20 and Women's World Cups in New Zealand and Canada. However, in what seemed like strange timing, the advance extract from Blatter's weekly column in a FIFA online magazine was released two hours after De Gregorio's exit was announced.
On Thursday, the European Parliament urged its member states -- which do not include Switzerland -- to "cooperate fully with all ongoing and future investigations on corrupt practices within FIFA."
However, Russia is not a member of the European Union, and its President Vladimir Putin has criticised American authorities for meddling in FIFA's affairs and seeking to have his country stripped of World Cup hosting. Russia and Qatar have consistently denied wrongdoing.
A FIFA investigation concluded last year that unethical behavior by most of the nine bid candidates did not affect the outcome of votes by FIFA's executive committee. Those December 2010 votes were the starting point of FIFA's current crisis, Blatter suggested last month.
He blamed American justice officials and media in England, noting that both countries were losing World Cup candidates.
Information from The Associated Press was used in this report.