Apple stock closed at its first record high of the year on Monday, helping lift U.S. indexes.
With a market capitalization of $3.89 trillion, the iPhone maker has overtaken Microsoft and lags only Nvidia as the most valuable U.S. company.
The shares ended Monday at $262.24. They edged higher in morning trading Tuesday.
They would need to hit $269.535 for Apple to be worth $4 trillion, according to Dow Jones Market Data.