Gamaa Islamiya and Islamic Jihad offered a truce where supporters of ousted Islamist president Mohammed Morsi will stop street protests if the military-backed government stops its violent crackdown on them.
The groups waged an Islamist insurgency in the 1990s.
Mr Morsi's allies have long refused to talk until the president is restored to power, but Islamic Jihad leader Mohammed Abu Samra said they had no "red lines."
However, the groups have no mandate to speak for the Muslim Brotherhood.
The offer comes as the Islamists' protest campaign is on the wane and numbers at their rallies are dwindling.
Brotherhood negotiator Amr Darrag said that his group is open for talks but only after "confidence-building measures."