By Lili Bayer, Gram Slattery, Andrew Gray and Fatos Bytyci BRUSSELS/WASHINGTON/TIRANA, June 30 (Reuters) - As NATO leaders prepare for a summit in Turkey next week, plans for an alliance summit in Albania next year have been thrown into doubt due to resistance from the Trump administration and dissatisfaction among NATO members with Tirana's low defence spending, a NATO diplomat, European official and three people familiar with the matter told Reuters.