The value of Norway's sovereign wealth fund officially hit $1 trillion early on Tuesday after outperforming all initial expectations, its manager said in a statement.

“I don't think anyone expected the fund to ever reach $1 trillion when the first transfer of oil revenue was made in May 1996,” said Chief Executive Officer Yngve Slyngstad of Norges Bank Investment Management, which operates the fund.

“Reaching $1 trillion is a milestone, and the growth in the fund's market value has been stunning,” he added.

A Reuters calculation, based on the fund's own live valuation on its website, had previously shown the fund hit the trillion-dollar mark on September 12.