Trinamool Congress chief Mamata Banerjee today declined to attend the dinner being hosted by UPA chairperson Sonia Gandhi in New Delhi on the eve of Presidential elections. Gandhi's political secretary Ahmed Patel rang up Banerjee inviting her to the UPA dinner on July 18 but the Trinamool Congress chief said she would be unable to attend, TMC sources said. The sources insisted it was not a boycott of the dinner but Banerjee would not be able to make it as she would be busy with a Trinamool Congress 'martyr's day' rally here on July 21 for which party workers would begin arriving from July 18.