The two leaders shook hands briefly but the warmth was clearly missing as Singh went about his business greeting others and later paying floral tributes to the portrait of Ambedkar.
Singh was seen chatting with Vice President Hamid Ansari with a bemused looking Advani sitting between the two leaders.
Advani has been attacking the Prime Minister calling him a "weak leader" in his campaign speeches for the Lok Sabha elections.
Singh took a swing at Advani saying that the BJP "iron man" was was quick to melt when held to the fire during the Kandahar hijacking incident.
Cong did not do justice to Ambedkar: Advani
BJP's prime ministerial candidate L K Advani said Congress did not do justice to Dalit icon Bhim Rao Ambedkar and ignored the late leader while nominating the members for the Constituent Assembly.
"I believe, Congress did not do justice to Dr Ambedkar," Advani said in a function to celebrate birth anniversary of the Dalit leader in New Delhi.
"Today, we know that he was the maker of the Constitution. But this did not happen naturally. When Congress nominated around 290 members for the Constituent Assembly, his name was not there," Advani said.
Taking on the Congress for the episode, Advani said that when a leader from Bengal saw that his (Ambedkar's) name was not there in the list, he offered his seat.
