This is going to be hard to explain….
Check it out:

President Obama was speaking with Italian PM Mario Renzi and Christine Lagarde, President of the International Monetary Fund. The Iraqi President Haider al-Abadi approached, clearly hoping to talk with Obama, sitting down right next to him. Obama continued his discussion with the others not acknowledging Abadi.

Obama and the others then stood up, and Abdadi stood as well, hoping to catch Obama’s attention, but Obama simply turned and walked away. Abdi and his translator then walk off, looking annoyed.