United States stocks have closed in positive territory as corporate raider Carl Icahn revealed a large stake in Apple, sending the technology titan 4.8% higher, and US retail data for July that was modest but helped boost the country's economic outlook.
The Dow Jones Industrial Average, whose 30 blue chip stocks do not include Apple, gained 31.33 (0.20%) at 15,451.01 points.
The broad-based S&P 500 climbed 4.69 (0.28 per cent) to close at 1,694.16 points.
The tech-rich Nasdaq Composite Index increased 14.49 (0.39 per cent) to 3,684.44 points.
Shares in Apple skyrocketed to finish at $US489.57 after Mr Icahn took to Twitter to disclose his "large" stake in the company, which he rated "extremely undervalued".
Mr Icahn reported having a "nice conversation" with Apple chief executive Tim Cook on a "larger buyback".
An Apple spokesman confirmed Mr Icahn and Mr Cook had "a very positive conversation".
The Commerce Department's monthly retail sales report came in lower than expected, with overall sales up just 0.2%, but the June figure was revised sharply higher to an 0.6% gain and July sales excluding autos were up a solid 0.5%, better than predicted.
Hugh Johnson, chairman and chief executive of Hugh Johnson Advisors, said investors were also reassured by comments from Federal Reserve Bank of Atlanta President Dennis Lockhart that suggested the Fed would take a cautious approach before scaling back its aggressive bond-buying program.