Purushothaman formally invited Thanhawla after the CLP leader submitted a letter staking claim to form the next government, Secretary to the Governor Ashutosh Kumar told PTI here.
The new Congress ministry led by Thanhawla would be sworn-in at the Raj Bhavan on Saturday, Kumar said.
It would be Thanhawla's second consecutive and fifth term as chief minister.
The Congress which has been ruling the state since the latter part of 2008 retained power winning 34 of the 40 seats in the Assembly in the elections held on November 24.
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In the later part of 1986, he vacated the chair to enable late erstwhile underground Mizo National Front leader Laldenga to be installed as chief minister in the MNF-Congress coalition interim government.
Thanhawla returned to power for a second time in 1989 when the Congress and MNF (Democrats) formed the government.
In 1993 he became chief minister for the third time when the Congress and Mizoram Janata Dal formed the government.
The Congress was defeated by the MNF in 1998 and in 2003.
The governor had yesterday dissolved the sixth Mizoram Assembly.