European Council President Donald Tusk delivers his speech during the EU leaders meeting on the 60th anniversary of the Treaty of Rome, in Rome, Italy March 25, 2017. REUTERS/Remo Casilli

BRUSSELS (Reuters) - The chairman of the European Union’s leaders, Donald Tusk, will go to Poland on April 19 to testify before a prosecutor as a witness in an investigation Poland has launched against two former military counter-intelligence chiefs.

“I can confirm that President Tusk, despite his legal immunity, will participate in the hearing on 19 April,” Tusk’s spokesman said.

Tusk is summoned as a witness and is not a defendant in the case.

The investigation is to establish if the two officials had all the necessary approvals, including from Tusk, who was then Poland’s prime minister, to establish cooperation with Russian intelligence on withdrawing NATO forces from Afghanistan.

Poland has contributed troops to the mission, which has used Russia’s transit hub of Ulyanovsk to bring people and equipment in and out of Afghanistan.