Western Digital Corp cut its offer for rival hard-disk maker SanDisk Corp by over $3 billion after China's Unisplendour Corp Ltd scrapped a deal to buy a stake in the company amid concerns about U.S. national security.

Unisplendour, a unit of China's state-backed Tsinghua Holdings Co Ltd, said in September it would buy a 15 percent stake in Western Digital for $3.78 billion.

The Chinese company scrapped the proposal after a decision by the Committee on Foreign Investment in the United States (CFIUS) to investigate the deal, Western Digital said.

"In some ways, not having the Chinese own 15 percent is a good thing for the combined business," an investor who has stake in both Western Digital and SanDisk said.

Western Digital shares were down 2.1 percent in early trading. Shares of SanDisk, which the latest offer values at $15.78 billion, were down 1.5 percent.

SanDisk did not immediately reply to requests for comment and Western Digital did not provide further details on the reason for the Chinese company's withdrawal from the deal.

Western Digital's move to proceed with the SanDisk deal comes after shareholder Alken Asset Management urged the company to scrap it, saying the price was too high.

Western Digital, which agreed to buy SanDisk for $19 billion in October, had said then it would revise the cash-and-stock offer if the Unisplendour investment fell through.

"Since the deal had been announced, Western Digital stock has underperformed significantly ... I think if you are a Western Digital shareholder the deal makes a lot of strategic sense," said Pacific Crest Securities analyst Monika Garg.

Based on Western Digital's Monday close, the company said it would now pay $78.50 per share in cash and stock for SanDisk, compared with its previous offer of $86.50.

Western Digital said regulators in the United States and European Union, among others, had approved the SanDisk deal.

CFIUS, an inter-agency panel led by the Treasury Department, assesses potential mergers to ensure they do not endanger national security. The agency's objections have created roadblocks for some Chinese deals.

Fairchild Semiconductor rejected an offer from China Resources Microelectronics Ltd and Hua Capital Management Co Ltd this month, citing concerns about U.S. approvals.