"BJP chief Rajnath Singh spoke to Shiv Sena chief Uddhav Thackeray this afternoon and has conveyed the decision in the matter," a top party official told IANS, declining to be named.
Rajnath Singh also sought the support of Thackeray and the Shiv Sena for Modi for the top position, the official said.
The BJP chief has also spoken to another major ally, the Akali Dal in Punjab, and conveyed the same decision to its leaders.
Though full details of what transpired between Rajnath Singh and Thackeray were not yet known, Friday's call was a follow-up of a similar telephonic conversation between Modi and Thackeray late Thursday.
After that, the Shiv Sena Friday openly declared its support for Modi or "any other candidate" named by the BJP for the country's top executive post.
Modi's name is likely to be announced later in the day by the BJP for the country's top post but, it seems, the Shiv Sena was sitting on the fence on the issue of supporting him. In the past it had rooted for Modi's party colleague Sushma Swaraj as the BJP's prime ministerial nominee.
Shiv Sena MP and spokesperson Sanjay Raut said the late Bal Thackeray had blessed Modi's candidature for the post of prime minister.
To a question on the reported friction within the BJP with a section of top leaders unhappy over the decision, Raut said that "it's an internal matter of the BJP and we cannot comment on it".