May 15 (Reuters) - Bill Ackman's hedge fund Pershing Square will disclose a new position in Microsoft MSFT.O later in the day, the billionaire investor said on Friday, arguing that the tech giant sits at a "highly compelling valuation".

Ackman's new closed-end fund Pershing Square USA PSUS.N, which debuted on the NYSE last month, has also recently made Microsoft a core holding, he said in a post on social media platform X.

Pershing's bet on Microsoft comes amid Ackman's growing appetite for tech holdings. In February, he said Pershing had bought shares in Meta Platforms META.O, betting the Facebook parent will benefit from artificial intelligence.

Last year, he made a new investment in Amazon AMZN.O and the firm previously invested in Alphabet GOOGL.O in late 2022.

Microsoft shares have fallen more than 15% so far this year, as investors worry that the company's early-mover advantage in the AI race is losing ground as Google and Amazon make strong progress in their own AI efforts.