TOKYO - S&P Global Ratings cut SoftBank Group Corp's long-term rating deeper into junk territory on Tuesday, leading the Japanese tech investment conglomerate to push back against the downgrade.

S&P lowered SoftBank's rating to BB from BB-plus, citing SoftBank's exposure to unlisted companies that are susceptible to changes in the external environment.

SoftBank has sold down assets including its stake in Chinese e-commerce giant Alibaba Group Holding Ltd to stabilise its balance sheet as the value of its portfolio falters.

"(Such sales) have eroded the proportion of listed assets in its portfolio. Furthermore, the technology stocks in which the company has primarily invested have been depressed for a prolonged period," S&P said in a note.

SoftBank CEO Masayoshi Son has pledged to play "defence" with prudent financial management amid weakness in tech valuations.

"It is extremely regrettable that our financial soundness was not properly assessed, and we will continue our dialogue with S&P," SoftBank said in a statement.

  - Reuters