On Saturday, the UN mission in Kabul appealed to the abductors to "show their humanity" by releasing him and his colleagues.
"Mr Mastrogiacomo is a well-known journalist whose sympathies for the people of Afghanistan should be beyond doubt to anyone," a UN spokesman said in a statement.
The La Repubblica reporter and his two colleagues were seized in the southern province of Helmand and the Taliban claimed that he had confessed to spying for British troops.
Massimo d'Alema, the Italian foreign minister, asked on Friday for more time to negotiate Mastrogiacomo's release.
"The complex affair ... needs time," he said.
D'Alema denied that the Italian government was negotiating with the Taliban, but said that contact had taken place via "humanitarian sources".
"Even the other side has perceived that an initiative is under way to find a solution," D'Alema said, without naming the Taliban.
"I want the other side to understand that the situation needs a reasonable time to develop and obtain the desired results."
The Taliban had said that the Italian and his Afghani translator would be released if the Kabul government agreed to release three Taliban prisoners.
Mastrogiacomo appeared in a video, released on Wednesday, appealing to the Italian government to work for his release.