No official meeting between Obama, Erdogan in Washington this week

Following reports that Turkish President Tayyip Erdogan was "humiliated" by US President Obama's refusal to hold an official meeting with him during this week's Nuclear Security Summit in Washington, White House spokesman Josh Earnest said Tuesday that he expects Obama "will have an opportunity at some point to have at least an informal discussion" with Erdogan during the event. Earnest said no official meeting was scheduled due to the large number of visiting heads of state. Erdogan is already scheduled to meet with Vice President Joe Biden during the summit, which will be attended by more than 50 world leaders. 
The topic of nuclear security has gained renewed urgency after it was discovered that the terrorists who carried out the attacks on Brussels last week spied on a senior Belgian nuclear researcher.