TOKYO, April 9 (Reuters) - The chairman of Toshiba Corp's board said on Friday a recent $20 billion offer by CVC Capital Partners to take the company private was contingent on various regulatory approvals and financing arrangements, suggesting any deal would take time.

"This initial proposal by CVC was completely unsolicited and not initiated by Toshiba," board chairman Osamu Nagayama said.

The offer comes three weeks after shareholders approved an independent investigation into the scandal-hit company.

Going private could help shield Toshiba and Chief Executive Nobuaki Kurumatani, who joined the company from CVC, from increasing pressure by activist shareholders who are demanding better governance.

Analysts have also warned of tough regulatory reviews, as Toshiba's business includes building nuclear reactors, supplying defence equipment and lithium-ion batteries used in submarines.

Nagayama said that CVC's proposal was contingent on financing assistance from co-investors and financial institutions.

"We expect that such a financing process would require a substantial amount of time and involve complexity for consideration," he said.

The Nikkei financial daily said state-backed Japan Investment Corp (JIC) and the Development Bank of Japan (DBJ) would join CVC's bid.

Both JIC and DBJ declined to comment.

CVC planned to launch a tender offer around early July and aimed to delist the shares in October, the Nikkei said.

Toshiba is expecting CVC to present a formal proposal as early as next week, which will be examined by a special committee made up of external directors, according to a source familiar with the matter.

The source, declining to be identified as the matter is private, said that CVC was offering about 5,000 yen per share, a 30% premium on their earlier value.

Toshiba shares fell 5.4% to 4,265 yen on the Tokyo Stock Exchange after the chairman's statement prompted investors to take a cautious view of a deal coming together.

Dozens of activist funds took stakes in Toshiba when the company sold 600 billion yen ($5.48 billion) of stocks in 2017 during a crisis stemming from the bankruptcy of its U.S. nuclear power unit. ($1 = 109.4200 yen) (Reporting by Ritsuko Ando, Makiko Yamazaki and Noriyuki Hirata; Editing by Himani Sarkar, Christopher Cushing and Ana Nicolaci da Costa)