Reuters, Istanbul :The last time U.S. Vice President Joe Biden flew to Turkey, in January, he had a stern message for President Tayyip Erdogan: his model of Islamic democracy was setting a bad example by intimidating media and threatening academics.But his tone was markedly different when he arrived in Ankara on Wednesday, weeks after a failed coup in Turkey that has strained relations between the two countries, and he appeared to be in diplomatic damage-limitation mode.Turkish officials have been incensed by the concerns expressed by Washington and European capitals about Ankara’s subsequent crackdown on suspected plotters, but what they perceive as indifference to the coup attempt itself. A weakening of the U.S.-Turkish alliance is a concern for the United States, which is counting on support from Turkey – which has NATO’s second-biggest military – in the battle against Islamic State.American worries may have been compounded by Erdogan restoring ties with Russia and even discussing military cooperation with President Vladimir Putin.Meeting with Erdogan and Turkey’s prime minister in Ankara on Wednesday, Biden delivered a message of alliance and conciliation.”Let me say it for one last time: The American people stand with you … Barack Obama was one of the first people you called. But I do apologize. I wish I could have been here earlier,” Biden said.He said U.S. officials would cooperate in investigating evidence against Fethullah Gulen, the U.S.-based cleric Erdogan has blamed for masterminding the coup bid with his followers. Erdogan has demanded that Washington hand over Gulen, who has denied any involvement in the coup, but U.S. authorities have said Turkey must first provide evidence of his wrongdoing.Hours before Biden arrived, in a timely illustration of the role Turkey plays in the fight against Islamic State, Turkish forces backed by U.S.-led coalition jets launched a major push across the border into northern Syria to drive the jihadist group out of the frontier town of Jarablus.