Blatter describes Obama in a letter as a ''visionary leader and unifier.'' Blatter, who was 75 in March, tells Obama that ''turning 50 is an occasion to reflect and look forward.''
Both leaders, who met at the White House two years ago, have experienced tough summers. Blatter has defended FIFA against numerous corruption allegations and Obama brokered a deal to avoid defaulting on national debts.
Blatter writes ''I wish you strength in these difficult times and I am convinced that you ... will succeed in overcoming these challenges.''