When questioned, state BJP spokesperson Madhav Bhandari declined to make any specific comment, but asked the media to pose the question to Sena why it would not attend the NDA conclave tomorrow.
The development comes barely six days after the Sena withdrew its sole nominee in the Union Cabinet, Minister for Heavy Industries Arvind Sawant.
The second biggest group supporting the NDA after the BJP, the Sena has 18 Lok Sabha MPs and had been a constituent of the NDA during the tenure of former Prime Minister Atal Bihari Vajpayee, and later in the first term of Prime Minister Narendra Modi, and the first six months of Modi's second tenure.
However, after a bitter public brawl over the post of Chief Minister and other power-sharing squabbles with former CM Devendra Fadnavis and others, the Sena is now charting a new course by preparing to form the Maharashtra government with the NCP-Congress, stunning the BJP.
On Sunday, NCP President Sharad Pawar and Congress Interim President Sonia Gandhi are likely to have a crucial meeting to finalise the government formation in Maharashtra.
Political sources say it was "natural and wise" for the Sena to stay away from the NDA meeting to avoid sending conflicting signals to the Congress-NCP ahead of government formation.
Sunday also happens to be the seventh death anniversary of the Shiv Sena founder, Bal Thackeray, and the party has plans to commemorate it in a big way with a function at Shivaji Park and other memorial events all over the state.