New Delhi: Amid strains in ties between the Congress and the Trinamool Congress, Prime Minister Manmohan Singh will host a dinner for United Progressive Alliance (UPA) constituents here on Tuesday.

The dinner was originally scheduled for today but it has now been postponed till tomorrow, sources said.

Singh has invited leaders UPA constituents for the dinner to be held at his residence, they said.

The dinner by the Prime Minister for UPA allies comes in the backdrop of Trinamool Congress leader and West Bengal Chief Minister Mamata Banerjee making common cause with non-Congress chief ministers on some issues, including FDI in retail and NCTC, and keeping the government on tenter hooks on her approach to non-UPA parties.

 Trinamool is the second largest constituent of UPA.

Banerjee was invited by SAD leader Parkash Singh Badal for the swearing-in ceremony on Wednesday and had earlier accepted this, a move seen as building pressure on the government.

However, she has now relented and decided to send some representatives of her party to the event. Her change in decision comes after Congress said on Sunday one should not cross the 'Laxman rekha' of 'coalition dharma'.

There have been murmurs of formation of a Third Front ever since Samajwadi Party won Uttar Pradesh polls.

However, Uttar Pradesh Chief Minister-designate Akhilesh Yadav on Monday said there was no move as of now to form such a Front and termed his invitation to West Bengal and Tamil Nadu Chief Ministers for his swearing-in ceremony as part of established traditions.