Both Mamata Banerjee and Mayawati been avoiding close association with the Congress

At least three key opposition leaders - Mamata Banerjee, Mayawati and her ally Samajwadi leader Akhilesh Yadav - are likely to skip the post-election opposition meet in Delhi that will be hosted by the Congress.

Sources said Andhra Pradesh Chief Minister Chandrababu Naidu, who had gone to Bengal last week and met Mamata Banerjee, received a negative when they discussed the meet. There is no need for any meeting before the results come out on May 23, she told Mr Naidu, sources said. Negative responses have also come from Mayawati.

The reason, sources indicate, is the inevitable question of the Prime Minister's post in case of a favourable result for the opposition. While all opposition leaders have so far carefully avoided questions on the top job for the sake of unity, both Mayawati and Mamata Banerjee harbor prime ministerial ambition. Congress chief Rahul Gandhi's name has already been proposed for the post by several leaders, including DMK chief MK Stalin.

Both have been avoiding close association with the Congress, staying out of an alliance with the Congress in their states, even if they are allies at the national level.

Mayawati has made no secret of her disdain of the Congress. Not only has she left the party out of the Uttar Pradesh alliance, over the last five months, she has repeatedly threatened to pull the rug from the Kamal Nath government, which has a wafer-thin majority in Madhya Pradesh.

Yesterday, she had targeted the government of Ashok Gehlot over the rape case in Rajasthan's Alwar. "We want the Supreme Court to act against the Congress, the police and the state administration and punish them as strictly as possible," she had said.

Last week, Mayawati gave the clearest yet hint of her national ambition, saying she "may have to" contest the Lok Sabha election from Uttar Pradesh's Ambedkar Nagar "if all goes well".

Mamata Banerjee, a veteran of more than 30 years in politics, has not spoken openly of her ambition for the top job. But her party leaders have said enough to draw jabs from Prime Minister Narendra Modi.

Speaking from Mamata Banerjee's home turf, Bengal, PM Modi had said, "Anyone fighting on 40 seats, 20 seats, 25 seats, says he wants to claim the prime minister's post. Sab ghungroo bandhke taiyar ho gaye (everyone is ready, with bells on, to take the post)".

Despite Mayawati's frequent attacks, Congress chief Rahul Gandhi has called her a "national symbol". "I respect her, love her. Sure we have a political fight and we fight for the ideology of the Congress... (but) I respect her contribution to the country," Mr Gandhi has said in an interview to NDTV.

While Rahul Gandhi had made no such statement on behalf of Mamata Banerjee, he has toned down her rhetoric against the Bengal leader, who, after one of his scathing attacks, had dismissed him as a "young lad".

Ms Banerjee has also kept alive her links with Telangana Chief Minister K Chandrashekar Rao, who is batting for a non-Congress, non-BJP front to rule at the Centre, with a Prime Minister from a southern state.