Very low-fidelity DNA ligase that seals nicks in double-stranded DNA during DNA repair (PubMed:15938630). Together with the viral repair DNA polymerase X, fills the single nucleotide gaps generated by the AP endonuclease (PubMed:15938630). It is not essential for viral replication and recombination (PubMed:15938630). Displays a very low adenylation activity towards DNA with 3'-dideoxy- or 3'-amino-terminated nicks compared to regular nick DNA (PubMed:15938630). ATP + (deoxyribonucleotide)n-3'-hydroxyl + 5'-phospho-(deoxyribonucleotide)m = (deoxyribonucleotide)n+m + AMP + diphosphate. Found in association with the viral nucleoid. The N-terminus domain (NTD) plays a critical role in DNA-binding, catalytic complex assembly and catalysis. Consistent with its intracellular location, ASFV encodes its own replicative DNA polymerase and three base excision repair enzymes: a class II AP endonuclease, the repair polymerase Pol X, and an ATP-dependent DNA ligase. Belongs to the ATP-dependent DNA ligase family.