CVS Health Corp. is moving closer to a deal to buy Aetna Inc. for more than $66 billion in cash and stock. The deal, which could be announced by Monday, would create a health-care behemoth selling everything from drugs to insurance.

The companies are in advanced stages of negotiating a deal, according to people familiar with the matter. It would likely be valued at between $200 and $205 per Aetna share and consist mainly of cash, some of the people said.

The cash-stock mix has yet to be finalized, and Aetna has been pushing for more cash, they added.

It is still possible the timing could slip or that the companies will fail to reach a deal.

Aetna shares edged up to $180.18 on Thursday. The stock was trading at about $160 when The Wall Street Journal reported on the possibility of a deal with CVS on Oct. 26; on that basis, a price of over $200 a share would represent a premium of more than 25%.