"We cannot grant you accreditation due to a large number of applications," the PACE press service said.
Assange will give testimony about his detention and conviction in the United Kingdom before the PACE Committee on Legal Affairs and Human Rights in what will be his first public appearance after his release from a high-security London prison on June 25.
Assange, an Australian citizen, was freed after spending more than five years in jail on bail breach charges. In the United States, he faced prosecution under the Espionage Act for obtaining and disclosing classified information that shed light on war crimes and human rights violations committed by US troops in Iraq and Afghanistan.