How do you delay a job recruiter?

Both company A and B have shown interest in hiring me. I’ve gone on mulitple interviews with each of them. Company A is my 1st choice. Ive been told I will for sure hear from them on Tuesday.

I’ve been in email correspondance with company B. They asked what pay rate I was looking for, I gave them a figure, they countered with a lower number and the last email has left off with: ”Is that amount something you feel you would be able to work with?” and: ”We are hoping to make a final decision by the end of the week or monday of next week so I would appreciate a swift reply to this email as well”

I need to stall B until tuesday in case A falls through