New Delhi, April 20: Bihar chief minister Nitish Kumar today called on Sonia Gandhi in the backdrop of efforts by many Opposition party leaders to forge anti-BJP unity and make a start of the coming together by fielding a joint Opposition candidate for the President of India's election in June.

The Janata Dal United (JDU) described Nitish's meeting with the Congress president as a "courtesy call" but sources said that the two leaders discussed the prospect of forging a wider Opposition unity and also fielding a joint candidate for the President's post.

"The two leaders discussed how different Opposition parties can work together," a JDU leader said under cover of anonymity.

Nitish, who was in the national capital to attend the wedding reception of Indian National Lok Dal (INLD) leader Dushyant Chautala, and met Sonia at her 10 Janpath residence .

"The Congress president was very keen to meet Nitish. The two leaders had not met for a long time," the JDU leader said.

Nitish, who has been advocating the need for "maximum Opposition unity" to fight the BJP, is also of the opinion that the non-NDA parties should field a common candidate for the presidential election due in June this year, the JDU said.

"We want one name for the presidential election that will supported by all non-NDA parties," said JDU leader K.C. Tyagi.

"We have urged Congress president Sonia Gandhi to take the lead and talk to leaders of different parties to evolve a consensus."

The Bihar chief minister has already met leaders of parties like the Nationalist Congress Party (NCP), the Left parties and also the Biju Janata Dal in his effort to unite the Opposition.

The Bihar chief minister, sources said, was keen to be projected as the leader of the united Opposition block and so he was taking the lead in reaching out to various party leaders.

JDU leaders believe that Nitish is the only credible face to take on Narendra Modi at the national level.

His meeting with Sonia assumes significance, given the Congress's eagerness to project Rahul Gandhi as the challenger to Modi.

JDU leaders, however, feel that given the continuous downward slide of the Congress under Rahul he can hardly match the Modi magic.

"The Bihar chief minister is the only credible alternative to Modi," said a JDU leader.

"Under his leadership only, the Modi wave collapsed in Bihar and it can be repeated in the country if the Congress and all other Opposition parties declare Nitish the face (of the non-BJP front).

It was not clear whether Sonia and Nitish discussed the leadership issue of the Opposition block.