WARSAW (AFP) – EU president Donald Tusk heads to Warsaw on Wednesday to testify before prosecutors in an investigation into two former military counterintelligence chiefs. The former Polish prime minister tweeted earlier this month that he would attend: “(April) 16 – holidays at home, 19 – prosecutor’s office in Warsaw, 22 – my 60th (!) birthday. What a marathon. See you on the road :)” Tusk had been summoned for the closed-door questioning in March but was unable to appear due to a previous commitment at the European Parliament. The probe centres on Generals Janusz Nosek and Piotr Pytel who are suspected of having “overstepped their duties by collaborating with services of a foreign state” without authorisation. According to Polish media reports, at issue is an agreement struck with Russia’s FSB intelligence service — the successor to the KGB — shortly after a 2010 air disaster in Russia which killed then Polish president Lech Kaczynski and scores of senior Polish statesmen. Tusk was prime minister at the time. Some reports suggest the agreement was aimed at cooperating on the withdrawal of Polish troops from NATO operations in Afghanistan at the time, while others say it allowed FSB agents to visit Polish SKW