Who also made us sufficient for such confidence (ος κα ικανωσεν ημας). Late causative verb from ικανος (verse 2. Corinthians 3:5) first aorist active indicative, "who (God) rendered us fit." In N.T. only here and Colossians 1:12.

As ministers of a new covenant (διακονους καινης διαθηκης). Predicate accusative with ικανωσεν. For διαθηκη see on Matthew 26:28 and for διακονος on Matthew 20:26 and for καινης (fresh and effective) on Luke 5:38. Only God can make us that.