Nov 27 (Reuters) - ChatGPT-owner OpenAI is allowing its

employees to sell roughly $1.5 billion worth of shares in a new

tender offer to Japan's SoftBank Group, two sources

familiar with the matter told Reuters on Wednesday.

SoftBank's billionaire CEO Masayoshi Son has been

persistent in seeking a larger stake in the startup after

investing in the last funding round, according to CNBC, which

first reported the news.

The Microsoft ( MSFT )-backed artificial intelligence start-up

raised $500 million from the Japanese conglomerate, according to

a media report, in a $6.6 billion funding round in October at a

valuation of $157 billion.

OpenAI employees will have until Dec. 24 to decide if they

want to participate in the new funding round, a source told

Reuters, adding that the stock's offer price aligns with the

company's last funding round. The investment will come from

SoftBank's Vision Fund 2, another source said.

The sources declined to be named as they were not

authorized to speak to the media. SoftBank and OpenAI declined

to comment.

Son has been pushing to expand his conglomerate's exposure

to the AI wave, taking a stake in OpenAI and acquiring chip

startup Graphcore.

He recently said that he was saving up funds "so I can

make the next big move," but did not provide any details about

his investment plans.

OpenAI's meteoric rise in terms of product popularity and

valuation has captured the world's imagination. Since the launch

of ChatGPT, it has attracted 250 million weekly active users.

(Additional reporting by Shubham Kalia in Bengaluru; Editing by

Abinaya Vijayaraghavan)