Edward Snowden’s father has said he is reasonably confident the whistleblower will return to the US if certain conditions are met.

In an interview with NBC, Mr Snowden's father also said he plans to make that point in a letter to US Attorney General Eric Holder later today.

Those conditions could include not detaining Mr Snowden before trial, NBC reported.

In the interview, Mr Snowden's father also expressed fears his son is being manipulated by others, including WikiLeaks.