President Biden Invites Ukraine President To The White House

The White House plans to address certain issues this summer, but only after President Biden's trip to Europe. Ukrainian President Zelensky expressed his desire to meet with Biden before Biden's meeting with Russian President Putin. Zelensky believes it would be a significant diplomatic mistake not to meet with him before the summit with Putin.

What may affect the timing of the meeting between Biden and Zolensky?

What is the significance of the upcoming summit mentioned in the text?