Amazon has boosted spending in particular to help develop artificial intelligence software. The company's sales estimate for the first quarter failed to meet analysts' expectations, even if a negative impact of US$2 billion from last year's Leap Day is included. The company said it anticipates between US$151 billion and US$155 billion, compared with the average estimate of US$158 billion. The cloud unit, Amazon Web Services, reported a 19 per cent rise in revenue to US$28.79 billion, falling short of estimates of US$28.87 billion, according to data compiled by LSEG. Amazon joins smaller cloud providers Microsoft and Google in reporting weak cloud numbers. Chief Executive Officer Andy Jassy said the inconsistent flow of computer chips had held back some growth in AWS. "We could be growing faster, if not for some of the constraints on capacity, and they come in the form of chips from our third-party partners coming a little bit slower than before," he told investors on a conference call.