The CPI-M said Friday it will watch the proposed united front of socialist parties before deciding whether to join it or not.
"It is too early to decide ... because their process is still in the initial stage and is yet to take a concrete shape," Communist Party of India-Marxist leader Sitaram Yechuri told the media here.
He said his party's priority was to strengthen the Left forces and unite them.
"More than anything, a unity of Left forces is important to counter communal forces."
Ahead of the winter session of parliament, leaders of the Samajwadi Party, Janata Dal-United, Rashtriya Janata Dal and Janata Dal-Secular have announced a united front to counter the Narendra Modi government.
Left parties were not invited to the meeting.
