Mr Mahmood is currently posted as Pakistan's ambassador to Turkey and is expected to arrive in Islamabad next week.
"His appointment to India will be announced once it is formally approved by Prime Minister Nawaz Sharif who has also the additional charge of foreign minister," sources in the Pakistan Foreign Office said.
Mr Mahmood would take responsibilities as High Commissioner from early next month, according to the sources.
Mr Mahmood will replace Mr Basit who has already completed his three-year tenure in New Delhi. Mr Basit is likely to be appointed as head of Foreign Service Academy (FSA) in Islamabad.
Mr Basit had earlier threatened to resign after he was overlooked and his junior Tehmina Janjua was appointed as Foreign Secretary. Initially, it was expected that Mr Basit might go on a long leave after he was called back from New Delhi but now he is expected to join as chief of FSA.
In a related development, Javed Nasarullah, current ambassador to South Korea, is likely to be appointed as new ambassador to Afghanistan. He will replace incumbent Syed Ibrar Hussain who is being appointed as Special Secretary in the Foreign Office.