* China has not yet given its antimonopoly approval
* Toshiba has option to ditch sale if not closed by March 31 -sources (Adds background)
TOKYO, March 26 (Reuters) - Japan's Toshiba Corp said on Monday it had yet to receive clearance from all regulators for the sale of its prized $18 billion memory-chip business by its self-imposed end-March deadline, but added it aimed to sell it as early as possible.
The conglomerate agreed last year to sell the world's second-biggest producer of NAND flash memory chips to a consortium led by U.S. private equity firm Bain Capital to plug a financial hole left by the bankruptcy of its U.S. nuclear unit.
It had faced a March 23 deadline to win approval from antimonopoly authorities to sell the business by March 31, but China has not yet given its approval.
In a statement, Toshiba said it had yet to confirm regulatory approval from all authorities, without naming China.
"We do not yet know when the transfer will be completed, but we will continue to aim for the sale soon," Toshiba said. A spokesman said the company had not yet given up on closing the deal by the end of this month.
A source with direct knowledge of the matter said last week antitrust approval must come by early this week to meet the deadline.
Toshiba no longer faces immediate insolvency or a delisting even if it does not meet the end-March deadline, as it raised funds from a share issue late last year.
Missing the deadline for the sale of the chip unit to the Bain consortium would give Toshiba the option of walking away without penalties, people briefed on the matter said.
Some activist shareholders oppose the sale saying that the $18 billion price tag undervalues the business and Toshiba should renegotiate with the Bain group or consider an IPO. (Reporting by Chang-Ran Kim and Makiko Yamazaki; Editing by Stephen Coates)