President Barack Obama has said he expects the UK to remain a major contributor to European security and that it will be able to agree an "orderly transition" with the EU.
"I have no doubt that the UK will remain one of Nato's most capable members," he told the FT as alliance leaders gather for a summit.
The meeting will focus on the perceived threat from a resurgent Russia.
But it has been overshadowed by the UK's vote to leave the EU.
Obama warns on Brexit talks
Mr Obama met European Council President Donald Tusk and European Commission President Jean-Claude Juncker on Friday and told a news conference that the Brexit vote had created uncertainty over the future of European integration.
But he rejected as misplaced hyperbole any suggestion that the Brexit vote signified the crumbling of the entire edifice of European security.
While he was confident the EU and UK would work together in a pragmatic fashion, he warned that "no-one has an interest in protracted adversarial negotiations".
"Everybody has an interest in minimising any disruptions as the UK and the EU forge a new relationship," he said.
Nato Secretary General Jens Stoltenberg said he was certain that the UK and the EU would find a way to co-operate and that the UK would remain a strong and committed ally in Nato.
Prime Minister David Cameron was later expected to underline the UK's commitment to Nato in the wake of the UK referendum, with a commitment to meeting the alliance's target of spending 2% of GDP on defence.
Nato will agree on Friday to bolster the Western military alliance's defences next year with four multinational battalions in Estonia, Latvia, Lithuania and Poland made up of some 3,000 troops from the UK, US, Germany, and Canada. Nato members made the decision after Russia's annexation of Crimea from Ukraine in 2014.