Mr Erdogan called on the king of Saudi Arabia, one of the Arab and Muslim countries that severed ties with Qatar, to resolve the crisis.
Saudi Arabia's foreign minister insisted there is no blockade on Qatar and says his country will provide food and medical supplies if needed.
He reiterated his country's position to support Qatar and diplomatic engagement to help end the crisis in a speech to party members on Tuesday.
He said that Qatar has "practically been sentenced to the death penalty" and added that "it is neither humane nor Islamic to attempt to isolate a country's people in every area from food, to drink, to travel, to commerce, to worship".
Senior Airman Steven Engels, 379th Expeditionary Aircraft Maintenance Squadron crew chief, marshals a C-130 Hercules on the flight line June 28, 2016, at Al Udeid Air Base, Qatar. This month, nine countries in the Middle East cut off diplomatic ties with Qatar because of the issue.
"How will you be a mediator if you are taking sides? Turkey has maintained good relations with Qatar as well as several of its Gulf Arab neighbours.
Turkey and Qatar have both provided support for the Muslim Brotherhood in Egypt and backed rebels fighting to overthrow Syrian President Bashar al-Assad.
Erdogan, who has long tried to play the role of a regional power broker, said Ankara would do everything in its power to help end the regional crisis.
Lawmakers from Erdogan's ruling AK Party and the nationalist opposition MHP were the main backers of the bill that allows troops to be deployed to Turkey's base in Qatar, but the main opposition CHP party said the timing sent the wrong message.