NATO in beginning a two-day summit in Wales that is expected to focus on the problems in eastern Ukraine and approve a plan to bolster NATO's presence along the alliance's eastern borders.
U.S. President Barack Obama and leaders of other NATO member states are meeting at Celtic Manor in south Wales to discuss a strategy to counter Russian moves in eastern Ukraine, where pro-Russian separatists have been on the offensive against Ukrainian government forces.
NATO says the separatists are supported by the Kremlin, a charge Russian officials have repeatedly denied.
Before the summit starts, Ukrainian President Petro Poroshenko is due to brief Obama and the leaders of Britain, France, Germany, and Italy about the situation in eastern Ukraine.
Ahead of the summit Obama traveled to Estonia, where he met with leaders of the three Baltic states: Estonia, Latvia, and Lithuania.
The three countries were once Soviet republics and have grown increasingly concerned at events in Ukraine.
Estonian President Toomas Hendrik Ilves said during Obama's visit that his country wanted NATO to set up permanent bases on its territory to protect it against potential threats from Russia.
Russia's annexation of Ukraine's Crimean Peninsula in March and the continued fighting between pro-Russian separatists and Ukrainian government forces in eastern Ukraine have led several former Soviet republics to seek closer ties with NATO.
Obama said in Estonia that the alliance also needed to do more to help NATO partners strengthen their defense, including Georgia and Moldova.
Georgian President Giorgi Margvelashvili says his country will ask for NATO membership at the alliance's upcoming summit in Britain.
Margvelashvili said in a speech at the Chatham House think tank in London on September 3 that "We will shoot for an invitation for NATO membership" but added that Tbilisi understood "[such] decisions are made in a much more complicated way.
Other topics on the agenda include how to confront the Islamic State militant group in Syria and Iraq and the withdrawal of NATO forces from Afghanistan.
One of the partner countries looking for NATO assurances against the militant threat is Uzbekistan, which has allowed NATO troops to use a base in Termez near the Afghan border and has been a key transit route along NATO's Northern Distribution Network into and out of Afghanistan.
Uzbek Foreign Minister Abdulaziz Komilov will attend the summit in Wales.