"Hamas rejects any one-sided change in the government without the agreement of all parties," Hamas spokesman Sami Abu Zuhri told AFP.
"No one told us anything about any decision to change and no one consulted with us about any change in the unity government. Fatah acted on its own in all regards."
Several senior officials said Tuesday that Abbas told members of his Fatah party that the Palestinian government would resign within 24 hours.
The move would signal a fresh setback in efforts to reconcile Gaza, dominated by Hamas, and the West Bank, where Abbas's Palestinian Authority is based.
It also comes as Israel and Hamas hold separate, indirect talks on ways to cement a long-term truce in the Gaza Strip following last year's 50-day war.
It's still unclear if the goal of Abbas' announcement regarding the government was meant to pressure Hamas and lead to concessions on various issues related to the functioning of the government, or if he truly intends to form a new government.
Elior Levy contributed to this article.