The bonds issued by two countries that have the same credit rating are highly likely to have the same credit spread

Sovereign credit ratings and corporate credit ratings adjust more quickly to new information about the borrower's creditworthiness than credit spreads do.

Both the market for a country's bonds and the market for CDS on the country's bonds can be used as sources of data to derive a credit spread for the country.

A sovereign CDS contract provides a payoff to the long position if a default or a credit migration of the reference entity occurs.