South Africa's president has 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".
His admission came as the country's biggest labour group urged him to resign.
The call by the Congress of South African Trade Unions, a traditional ally of the ruling party, increased pressure on President Jacob Zuma, who made his first public comments about last week's dismissal of finance minister Pravin Gordhan.
The firing deepened worries about government corruption and infighting.
South Africa's rand fell on Monday after Standard & Poor's, an international credit ratings agency, lowered the country to below investment grade, citing political instability and threats to economic growth.
In a speech in an industrial area of the capital, Pretoria, Mr Zuma thanked Mr Gordhan for assisting in the handover of the finance ministry to successor Malusi Gigaba, and he said the government "will do everything possible" to promote unity within its ranks.
"We know that public statements which indicate disagreements within government by ministers, for example, demoralise our people and create confusion," said Mr Zuma, who still commands significant support within the ruling African National Congress party despite growing calls for him to resign.
"This is a serious weakness and we shall attend to it within renewed vigour," the president said.
Mr Gigaba said the Standard & Poor's downgrade was a setback but noted what he described as the strengths of the South African economy, including increasing exports and a strong banking system.
The alliance between the ruling party and the trade union federation, or COSATU, has come under strain in the past.
On Tuesday, Bheki Ntshalintshali, the federation's general secretary, referred to Mr Zuma's "negligent leadership" and cited scandals including a Constitutional Court ruling against the president over millions of dollars in state spending on his private home.
"COSATU believes that he is no longer the right person to unite and lead the movement, the alliance and the country," Mr Ntshalintshali said, according to the African News Agency.
Some senior ruling party figures have also criticised the dismissal of Mr Gordhan, who generally received positive reviews for his strong anti-corruption stance and stewardship of one of Africa's biggest economies.
They include deputy president Cyril Ramaphosa, ANC secretary-general Gwede Mantashe and Zweli Mkhize, the party's treasurer-general.
Over the weekend, Mr Ramaphosa called for South Africans to get rid of "greedy" and "corrupt" people, though he did not mention anyone by name.
Emboldened opposition groups are planning demonstrations against Mr Zuma, hoping to capitalise on national discontent with the party that has led South Africa since the end of white minority rule in 1994.
The main opposition party, the Democratic Alliance, is pushing for a parliamentary vote of no confidence in Mr Zuma; previous votes have failed to dislodge him because the ruling party has a majority of seats.
The government has said social media calls to hold protests against Mr Zuma on Friday are designed to damage the country's image and economy.
It referred to messages that it said have called for a "shutdown of the country" and warned against any illegal protests that could lead to violence and destruction of property.