The bomb exploded 75 yards from the Hilton hotel entrance and shattered windows of nearby buildings. The officers had approached a package containing the explosives after an anonymous tip that a bomb had been placed nearby, the Police Chief said.
Bush will arrive in Ankara on 26 June and meet Prime Minister Recep Erdogan and President Ahmet Necdet Sezer the following day. The NATO summit in Istanbul is scheduled for 28 June.
Deputy Prime Minister Mehmet Ali Sahin confirmed security would be heightened after the blast. Turkish media reported that 7,000 police officers would be on duty in the capital for the Bush visit.
Security concerns in Turkey have risen since November, when four suicide truck bombings killed more than 60 people in attacks on two synagogues, the British consulate and an international bank.