May 5 (Reuters) - Slovakia's foreign minister offered his resignation on Friday, the president said, dealing a fresh blow to the centre-right cabinet which has already been serving in a caretaker capacity ahead of elections in September. Rastislav Kacer's departure follows a string of other ministerial resignations and piles pressure on Prime Minister Eduard Heger, who had been facing mounting opposition calls to quit and make way for a technocrat government. Caputova, whose role gives her the power to appoint a new prime minister, said she would discuss the situation with Heger and parliament speaker Boris Kollar on her return. SaS joined a leftist opposition party in voting through a no-confidence motion in December, accusing the government of not helping people cope with the higher energy costs. The prime minister said he would not comment until he meets the president.

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