Apple could surpass energy giant Exxon as the most valuable company in terms of market capitalisation.

According to The Associated Press, as soon as the total value of the iPhone maker's shares edges above those of Exxon's, Apple will take over the top spot in the Standard and Poor's 500.

The S&P 500 has been widely regarded as the best single gauge of the large cap US equities market since the index was first published in 1957, and is used by most professional money managers.

Billions of dollars invested in funds that track the index will have to shift their holdings to reflect Apple's new weighting according to AP's David K. Randall.

Apple's rise to the top suggests the market no longer holds traditional manufacturers, or those who rely on business spending or natural resources, in higher esteem than tech companies, Randall adds.

Apple iPhone 4

"If Apple becomes more valuable than Exxon, it will be only the second time that a growing technology company which doesn't pay dividends will make up the greatest share of the S&P 500," Randall reports. "The first, Microsoft Corp., held the position for two years in the late 1990s during the boom that made personal computers a staple in households around the world."

Randall notes, Apple shares cost around £4.42 just ten years ago, yet on Friday closed at £178. Apple has approximately £31.6 billion in cash sitting on the company's balance sheet.