Singh, who spoke to Tharoor last night soon after Sunanda's death, wrote a letter to his ministerial colleague to convey his condolences.
"It is with shock and deep sadness that I learnt about your bereavement. The loss of one's companion is indeed irreparable but I would like you to know that we are with you in this hour of grief. May God give you strength to tide over this difficult time," he wrote.
The body of the 52-year-old Pushkar, a woman entrepreneur who had married Tharoor in August, 2010, was found in mysterious circumstances yesterday at a luxury hotel in South Delhi.