EchoStar’s proposed deal to sell Dish Network to DirecTV — for $1 cash and the assumption of $9.75 billion in debt — is akin to Dish defaulting on its debt securities, according to credit-rating agency S&P Global.

As part of the deal, Dish Dbs announced a “subpar exchange offer” for various tranches of its debt totaling around $10 billion, S&P noted. In addition, Dish Network Corp. announced an offer to exchange $4.9 billion convertible notes for new securities alongside $5.1 billion of committed new money notes being issued.

“We view these transactions as tantamount to a default because investors will receive less value than the promise of the original securities,” S&P said in a note Tuesday. “Holders of existing Dish Dbs notes are being offered less than the original promise because the exchange rate as part of the mandatory exchange consideration into new DirecTV issuer notes is at a significant discount to par...