"Mr. Motlanthe will be responsible, for amongst other tasks, the coordination of Government Business," a statement from Mbeki's presidency said.

Motlanthe, a powerful ally of party leader Jacob Zuma, was appointed to South Africa's parliament in May as part of plans for him to enter government.

The former student activist, trade unionist and soldier in the ANC's disbanded military wing UmKhonto we Sizwe was elected the party's deputy president when Zuma became president in December last year.

The ANC executive had asked Mbeki to bring Motlanthe into cabinet to manage the transfer of power when Mbeki steps down at the expiry of his term next year.

Analysts believe bringing Motlanthe -- a left-leaning intellectual who is well-regarded in both the Mbeki and Zuma camps -- into government could help heal some of the differences that have developed between Mbeki's government and the Zuma-controlled ANC and allow for an easier transition in 2009.

Mbeki's hold on government is seen to be slipping as he draws closer to the end of his second and final term in 2009.

The South African leader has come under pressure from powerful unions and leftists who oppose his pro-business policies.

His worries also include a dire electricity shortage that threatens to trim economic growth and widespread criticism over his quiet diplomacy stance on dealing with the crisis in neighbouring Zimbabwe.

Zuma, who defeated Mbeki for the ANC leadership in party elections late last year, is the frontrunner to take over after general elections next April.

But a corruption trial hanging over his head could force Zuma to stand down from the presidential race, with some analysts suggesting Motlanthe could step in as a compromise presidential candidate if that happens.

Zuma was expected to go on trial in August for bribery, fraud and other wrongdoing in connection with an arms deal, but his lawyers say the start is likely to be pushed back for procedural reasons.