との (quotative + adnominal)

A compound marker: と (quotative) + の (adnominal/attributive), linking a quoted clause to a following noun. [quoted clause]+との+[noun] = 'a [noun] that says/states [clause].' すぐ来いとの便り ('a message saying come right away'), ~との報告 ('a report saying X'), ~との判断 ('a judgment that X'). Common in formal writing.