American officials are rushing to finalize details ahead of Friday’s summit talks between Presidents Donald Trump and Vladimir Putin in Alaska, with both logistical and geopolitical issues still unsettled four days ahead of the momentous sit-down.

For President Vladimir V. Putin of Russia, it is an opportunity not just to end the Ukraine war on his terms, but to split apart the Western security alliance.

NATO Secretary General Mark Rutte said Friday’s summit between President Donald Trump and Russian President Vladimir Putin in Alaska will be an important test in ending the war in Ukraine.