Former U.S. ambassador to NATO on the relationship between the alliance and Trump

+ Michel Martin NATO Secretary-General Mark Rutte, left, meets with President Donald Trump and other officials in the Oval Office on Wednesday in Washington.

+ Rutte met with Trump ahead of next month's NATO summit and as the Pentagon conducts a six-month review of U.S. forces in Europe. Andrew Harnik/Getty Images hide caption Former U.S. Ambassador to NATO Kurt Volker says European leaders expect next month's NATO summit in Turkey to proceed normally despite President Donald Trump's latest criticism of the alliance.

+ As NPR's Teri Schultz reported, NATO Secretary General Mark Rutte, who's visiting Washington this week, is under pressure to keep the 32-member alliance united after Trump suggested he might skip the summit if it were not hosted by Turkish President Recep Tayyip Erdogan, whom Trump has praised. Trump has also pressed NATO members to raise defense spending to 5% of their gross domestic product. Speaking to NPR's Morning Edition from Poland, where he is attending the Ukraine Recovery Conference, Volker said European officials remain frustrated with Trump but are encouraged by recent signs of continued U.S. support for Ukraine, including backing European purchases of American weapons. "Look, there is an overall deeply seated irritation and frustration with President Trump over everything, but within that they're kind of reading the tea leaves, saying, 'Where are we going? Where now?'" Volker said. He pointed to Trump's praise of Ukrainian fighters and continued U.S. backing for European purchases of American weapons as encouraging signals. Volker also said Ukraine has gained an advantage in drone warfare and Russia's economy has weakened. He expected the NATO summit would be "fairly smooth" and focused on defense spending and military procurement. Listen to the full interview by clicking on the blue play button above.