Convening in Berlin, Germany, Obama met with Germany's chancellor Angela Merkel, Britain's prime minister Theresa May, France's president Francois Hollande, Italy's prime minister Matteo Renzi and Spain's prime minister Mariano Rajoy.
The leaders concluded that sanctions against Russia must continue until Russia resolves its conflict with Ukraine. Obama and the EU claim that Russia has sent military and weapons to eastern Ukraine to aid separatists there.
The leaders also said that Syria and Russia must halt their attacks on Aleppo. "We agreed the need to keep up the pressure on Russia, including the possibility of sanctions on those who breach international humanitarian law," Britain's prime minister Teresa May said.
In regard to NATO, an official statement released by the White House after the summit said the leaders "affirmed the importance of continued co-operation through multilateral institutions, including Nato" and that they "agreed on the necessity of working collectively to move the transatlantic agenda forward, particularly on bringing stabilization to the Middle East and North Africa".
Despite the summit topics, Donald Trump has vowed to improve USA's relationship with Russia, and has criticized NATO as being outdated and unfair.
summit - an organized, regular meeting of international leaders
outgoing - leaving soon
affirm - to say something again as being factual
sanctions - penalty / punishment against a country by other countries
convene - to meet (officially)
separatists - people who fight to leave a country and start their own country or join another
halt - to immediately stop
outdated - old and not useful anymore