The Telugu Desam Party is likely to split in the Rajya Sabha with at least four of its six MPs tipped to break away and back the ruling BJP, sources said.
These MPs are likely to write to Rajya Sabha Chairman M Venkaiah Naidu about their decision, they added.
Their decision to back the BJP will give a boost to the saffron party in the Upper House as the ruling National Democratic Alliance does not have a majority there yet.
The sources said the breakaway faction may merge with the BJP and added that a final decision on the process is still being deliberated.
The TDP, which is led by former Andhra Pradesh chief minister N Chandrababu Naidu, has six members in the Rajya Sabha. If four of them break away, then it will meet the legal requirement of anti-defection law, which mandates the support of at least two-third members for a split to be recognised in Parliament.
The Rajya Sabha has a strength of 245 members and the BJP is the single largest party with 71 MPs.