KYIV (Reuters) - Ukrainian investigators formally notified the head of Ukraine’s constitutional court that he is a suspect in a witness tampering case, the state investigation bureau said on Tuesday. Ukrainian prosecutors said in December they were investigating Oleksandr Tupytskyi in connection with the suspected bribery of a witness that had taken place in 2018. “I believe that this criminal case is falsified and politically motivated, and the investigation is conducted in violation of the principle of objectivity and impartiality,” Tupytskyi said in a statement. “I am confident that the purpose of this case is an attempt to prevent me from exercising the power of a judge and the head of the constitutional court ... as well as to block the activities of the Constitutional Court of Ukraine.” President Volodymyr Zelenskiy’s administration has been locked in a standoff with the top court after it struck down key anti-corruption legislation in October, hobbling Ukraine’s chances of securing foreign aid loans. Zelenskiy had initially sought to dissolve the court but parliament restored the anti-corruption legislation as an interim measure in December, paving the way for loan talks to restart with the International Monetary Fund. Zelenskiy also signed a decree to suspend Tupytskyi temporarily, which the court said was unconstitutional. Tupytskyi’s office said in an earlier statement on Tuesday that law enforcement officials prevented him from entering the court premises. The court ruled in October against some anti-corruption laws, citing as excessive the punishment for false information on officials’ asset declarations, and also struck down some powers of the main NAZK anti-graft agency. Ukraine’s patchy performance on economic reforms and tackling corruption derailed a $5 billion programme agreed last June with the IMF, at a time when its economy is in a sharp downturn due to the coronavirus pandemic.