Iranian opposition leaders Mir Hossein Mousavi and Mehdi Karroubi are under house arrest. Both were detained shortly after making requests early this year to have public demonstrations. Mousavi was the top challenger to Iranian President Mahmoud Ahmadinejad, whose re-election in 2009 sparked violent protests in Iran.
Some Iranian lawmakers accused Karroubi and Mousavi of treason and called for their execution.
Khatami in a speech to veterans of the Iran-Iraq War in the 1980s advocated a spirit of reconciliation in the country, reports Radio Zamaneh, a Persian broadcaster in the Netherlands.
"If there has been any wrongdoing, let us all forgive each other and look toward the future," he was quoted as saying.
Meanwhile, Ahmadinejad is facing internal backlash over apparent disagreements with the country's Supreme Leader Ali Khamenei.
An Iranian newspaper last week said Khamenei called on the president to step aside over a series of spats over presidential allies, Bloomberg News reports. The president's office issued a statement saying "this news is wrong."