By Tuvan Gumrukcu ANKARA, June 30 (Reuters) - NATO is adjusting to a shifting security landscape and the United States is not seeking to leave the alliance, Turkish Defence Minister Yasar Guler told Reuters ahead of a NATO summit in Ankara next week. Turkey will host 32 NATO leaders, as well as officials from the Gulf and Asia-Pacific region, on July 7-8, amid tensions within the alliance over burden-sharing, defence spending, and U.S. complaints about allies' lack of involvement in re-opening the Strait of Hormuz.