President Jacob Zuma sacked Finance Minister Pravin Gordhan because their relationship had irretrievably broken down, the African National Congress (ANC) said on Wednesday.
Mantashe had also openly criticised Zuma's actions but on Wednesday, he painted a different picture, saying the ANC would "close ranks" around the president.
With the cabinet overhaul exposing deep divisions within the ANC, the main opposition Democratic Alliance party hopes to benefit at general elections in 2019.
Tomorrow, South Africans in their thousands will take to the streets to raise their voices against the ANC, Jacob Zuma and their mismanagement of the country.
The meeting acknowledged that Zuma's reshuffle had triggered the resurgence of the #ZumaMustFall movement‚ with many mobilising within government and the ANC to remove the president.
"The (party) has emphasised the need for unity of the ANC and the alliance in the interests of South Africa", Mantashe said.
"See you on the 18th" of April, he said when asked if he will be on Parliament on the day of a no-confidence vote in Zuma.
But the party's National Working Committee (NWC), discussing the cabinet reshuffle, has given the president its backing. South Africa's president on Tuesday responded to the political crisis that erupted after he fired the finance minister, acknowledging that public disputes at the top of the government are a "serious weakness", while the country's biggest labor group urged him to resign.
Cosatu General Secretary Bheki Ntshalintshali told a media briefing that the union's decision was driven by Mr Zuma's failure to consult it before making changes to his cabinet. No army anywhere in the world will subject their foot soldiers to be commanded by an enemy general.
The ANC says it calls on South Africans to rally around new ministers, who have invaluable skills and expertise, and assist them in their quest to make South Africa better.
While Zuma has survived a series of corruption scandals and presided over the party's worst-electoral performance since the end of apartheid in 1994 in municipal elections in August, the majority of ANC officials have stuck by him.
"The time has arrived for him to step down and allow the country to be led forward by a new collective at a government level", Cosatu said in a statement.
The opposition parties said ANC MPs should introspect "and choose Zuma and the Guptas - or the people".