"The Sena will support Pranab Mukherjee (in the Presidential polls)," said Sanjay Raut, Sena spokesperson.
According to Sena sources, the assurance to finance minister Pranab Mukherjee was given after he called up Sena supremo Bal Thackeray and his son, Uddhav Thackeray, party executive.
Reports reveal that Sena took the steps after its ally failed to finalise its candidate for the top Constitutional post.
Earlier, Shiv Sena had extended its support to President Prathiba Patil in 2007 for the post of President, as she belongs to Maharashtra, while NDA and BJP backed late Bhairon Singh Shekhawat.
NDAs dream to project former President Abdul Kalam fell flat after he formally announced that he would not contest for the race.
In a statement, Kalam said, "though I have never aspired to serve another term or shown interest in contesting the elections", the Trinamool Congress and other parties "wanted me" to contest.
"Many, many citizens have also expressed the same wish. It only reflects their love and affection for me and the aspiration of the people. I am really overwhelmed by this support. This being their wish, I respect it. I want to thank them for the trust they have in me," he said.
"I have considered the totality of the matter and the present political situation, and decided not to contest the Presidential elections 2012," Kalam added.
Meanwhile, the BJP is determined to not let the fight go unchallenged and met last evening to chalk out a plan. The final decision, will, however, be taken after the NDA meeting.