All India AnnaDravida Munnetra Kazhagam, a key partner of the newly-floated United National Progressive Alliance, is likely to vote for National Democratic Alliance-supported independent candidate Bhairon Singh Shekhawat in the presidential polls on Thursday.

All the party MLAs and Rajya Sabha members have been asked to assemble at the opposition leader's chamber at the state secretariat complex, where they will be told about the decision to support Shekhawat, AIADMK sources told PTI.

The MLAs, who were in their respective constituencies, were directed by party supremo Jayalalithaa to reach Chennai by Thursday morning, the sources added.

UNPA, in a recent meeting, had decided to abstain from voting in the presidential polls.

The AIADMK's move to vote for Shekawat signals the collapse of the UNPA, the coalition of regional parties, including Telugu Desam Party and Samajwadi Party, political observers said.

The Jayalalithaa-led party has 60 members in the Tamil Nadu assembly.