I am going to start a new job soon in another country. I was confirmed I was going to get hired one month ago, and at the time I gave my availability to start as soon as possible. We set a possible start date, but we had to wait for a number of checks and verifications before being sure of the date.
Since the date was approaching with no news, a few days ago I informed my future boss that without a quick confirmation it was becoming difficult for me to organise myself for moving. He is open and understanding, but also made clear that he prefers me to start at the earliest date possible.
The confirmation arrived 5 days before the start date, and I am asked to say tomorrow if I am ready or not for next week. While the thing is actually possible, it would be much easier for me to delay everything by one week.
On one hand, my boss was explicit about his preference, on the other hand, I was given only short notice. Would asking for a delay be unprofessional?