Get him thinking of something else. A friend of mine dealt successfully with such a situation. She talked him into going to a bar for another drink and then excused herself to go to the loo. Instead, she went to the manager s office and asked him to phone for a taxi for her. There are many ways to answer that question.
Every situation is unique and everyone has different capabilities.
I can, however, tell you what you can do to develop your own personal power for personal protection. Know who is in your space and what is really happening. If it doesn t feel right to you, something s wrong. Keep your center. Stay balanced and grounded, mentally and physically.