Iran is ready for a full prisoner exchange with the United States, Foreign Minister Mohammad Javad Zarif said.
More than 6000 were injured in the blast.
"We want to destroy and kill the government, they gave us no jobs or rights."
Protesters are calling for politicians to resign as the devastating blast compounds months of political and economic meltdown.
Lebanon's investigation into the blast will determine if it could have been caused by a bomb.
French President Emmanuel Macron has proposed a new political pact - but says it's up to local government.
The unknown substance was stored in the port for six years.
"You think these things don't happen to you."
At least 135 people are dead and thousands are injured.