The Vice President was speaking at the annual Munich Security Conference
US Vice President Mike Pence has reaffirmed support for NATO but warned other countries they need to ramp up spending.
He was speaking at the Munich Security Conference, which had earlier been opened by German Chancellor Angela Merkel.
He told the conference: "The United States of America strongly supports NATO and will be unwavering in our commitment to this trans-Atlantic alliance."
Mr Pence's address to the annual gathering of diplomats and security officials was part of an attempt to reassure sceptical allies in Europe about American foreign policy under Donald Trump.
He is due to go on and have a meeting with Ms Merkel and then sit down with leaders from Estonia, Latvia, Lithuania and Ukraine.
He is also expected to meet the prime minister of Turkey, another NATO member.
The speech and meetings come amid concerns about links between the Trump administration and Russia and fears about Kremlin aggression.
Earlier, the German Chancellor had said Europe's ties with Russia remained challenging, but it was important to work with Russia in the fight against Islamist terrorism.
She added that Germany would do "everything possible" to meet a NATO target for spending 2% of GDP on defence by 2024.
(Additional reporting from IRN)