WASHINGTON (AP) — President Joe Biden has invited Ukrainian President Volodymyr Zelenskyy for a White House visit this summer. The invitation comes as Zelenskyy has publicly expressed concerns about Biden’s plan to meet with Russian President Vladimir Putin next week at the end of the U.S. president’s eight-day visit to Europe. National security adviser Jake Sullivan said that Biden assured Zelenskyy in a phone call on Monday that the U.S. will “stand up firmly for Ukraine’s sovereignty, territorial integrity, and its aspirations as we go forward.” Zelenskyy has also raised concerns about a nearly completed Russia-to-Germany natural gas pipeline that would allow Russia to bypass Ukraine.