SAN FRANCISCO (AFP) - Apple on Tuesday posted record quarterly profit even as iPhone sales flattened out after years of rocketing growth.

Net income for the quarter ending Dec 26 was 2 per cent higher than the same period a year earlier at US$18.4 billion (S$26.2 billion), while revenue of US$75.9 billion set another record for the company.

"Our team delivered Apple's biggest quarter ever, thanks to the world's most innovative products and all-time record sales of iPhone, Apple Watch and Apple TV," Apple chief executive Tim Cook said in an earning release.

"The growth of our services business accelerated during the quarter to produce record results, and our installed base recently crossed a major milestone of one billion active devices."

Apple reported that, overall, a billion iPhones, iPads, Macintosh computers, iPod touch devices Apple TV units, and Apple Watch wearable computers had "engaged" with its services in the past three months.

Apple shares slipped slightly more than a percent to US$98.72 in after-market trades following release of earnings figures that showed iPhones that have been driving revenue for the California company showed the slowest growth since the lifestyle-altering handsets were introduced.

Apple said that it expected revenue in the current quarter to be between US$50 billion and US$53 billion.