A White House spokesman called it a “positive first step” towards denuclearising the Korean peninsula.
China and Russia also welcomed the move, while Japan said it could “be seen as progress”.
The deal followed talks between US and North Korean diplomats in Beijing last week.
The US has announced 240,000 tonnes of new food aid for Pyongyang in return for the freeze.
North Korea confirmed the suspension in a foreign ministry statement released in Pyongyang on Wednesday.
It said the move “aimed at building confidence for the improvement of relations” between the two countries, and said talks would continue.
In Washington, the feeling among officials and analysts is that this is a useful but limited step forward.
Having inspectors on the ground in North Korea will, they believe, be very useful, but the optimism is coloured by a sense that promises like these have bloomed and withered many times in the past.
And what do the North Koreans get? They will receive shipments of “nutritional assistance” for a hungry population weeks before a politically important celebration – the anniversary of Kim Il-sung’s birth.
One crucial area not addressed, we’re told: uranium enrichment facilities which may exist outside Yongbyon. US analysts remain worried that North Korea possesses as yet undiscovered centrifuges.
The announcement comes two months after Kim Jong-un came to power following the death of his father, Kim Jong-il.