Antonyms for the phrase "am surety for" include "disclaim responsibility," "disavow," "repudiate," "renounce," "abjure," "deny," and "withdraw." These words suggest a refusal to take responsibility or liability for someone else's actions or debts. They indicate a lack of confidence in the ability of another person to uphold their obligations, and a desire to distance oneself from any potential consequences of their actions. While being a surety can be a noble act of trust and support, choosing to disavow responsibility may be necessary in situations where one's own welfare or reputation is at stake.