SoftBank Group Corp's creditworthiness "remains under pressure" despite moving to shore up its balance sheet by raising up to $41 billion via asset sales, credit-rating firm S&P Global Ratings said on Thursday.

There are questions over SoftBank's intention to adhere to "financial soundness and creditworthiness", S&P said, as the group undertakes an up to 2.5 trillion yen ($24 billion) share buyback programme, aimed at propping up its market valuation as investments via the $100 billion Vision Fund flounder.

In March, S&P revised its outlook for SoftBank to negative but stopped short of a ratings downgrade.

SoftBank has dropped S&P peer Moody's after it cut the tech conglomerate's rating further into junk territory and questioned the viability of its plan to sell down part of its portfolio.