Surging iPhone sales worldwide have earned Apple record-high profits for the fourth quarter as it prepares for its first major product launch since three years ago.

A doubling of iPhone sales helped Apple on Monday post record-high quarterly net profit of $3.38 billion in the fiscal quarter ending December 26.

"We're thrilled to report our best quarter ever," Apple chief financial officer Peter Oppenheimer said in a conference call with analysts.

Apple said revenue in the first quarter rose to $15.68 billion from $11.88 billion in the corresponding quarter a year ago.

"If you annualise our quarterly revenue, it's surprising that Apple is now a $50-billion-plus company," said the iconic California firm's chief executive officer Steve Jobs.

"The new products we are planning to release this year are very strong, starting this week with a major new product that we're really excited about," Mr Jobs said in a statement.

Apple has maintained trademark secrecy regarding an event at which it is expected to debut a tablet computer along the lines of an "iPhone on steroids," according to analysts.

The technology rumour mill is busy grinding speculation that the culture-changing firm has made a notepad-shaped tablet computer with a colour touchscreen that lets people browse the web, listen to music, watch movies or television shows and also read electronic books and newspapers.