Finance Secretary Kate Forbes has told BBC Scotland a budget deal may not be made this week.
In recent years, the Scottish government has reached agreement with the Greens before the first Holyrood budget vote. But Ms Forbes has made it clear that may not be the case this year.
MSPs are due to vote on the budget - in principle - this Thursday.
As a minority government, the SNP needs help from at least one rival party.
Ms Forbes said: "I think this year, we're in unprecedented circumstances. Not only is the budget delayed but there's also been a mini reshuffle as well.
"So, I'm optimistic that I will get the budget through but that doesn't mean it works to the same timetable as previous years."
She added that every party had said they were willing to work with her.
"I'll believe it when it comes to the votes but I do believe in compromise and I believe that we will work hard to get a deal," she said.
"Government is certainly willing to speak to any party that have reasonable suggestions to make and our challenge will always be finding the money to meet their demands."
She said opposition parties would have to help identify where the money would come from before she could agree to changes.
"Every penny has been deployed which is the challenge of going ahead of the UK government's budget," she added.
"So, last year additional consequentials were found. Those were late consequentials. You can't have late consequentials when you don't have the UK government budget yet."
Parties have until next Thursday to find a compromise.