ISTANBUL Polish Prime Minister Donald Tusk vowed Thursday to deliver a "ruthless" response to any attempt by newly sworn-in conservative President Karol Nawrocki to interfere in his government’s work, according to media reports. "Wherever he wants to interfere, he will see what the constitutional rule is all about, that is, who governs in the country, and I will be very consistent in this matter, and if necessary, also ruthless," Tusk said at a news conference, broadcaster TVP World reported.