The issue was raised by opposition members as soon as the house met, forcing a brief adjournment.
Opposition members complained that the statement given by Modi at a recent party function differed from what has been said by Sitharaman in the house.
Finance Minister Arun Jaitley denied it and said: "There is no difference in what commerce minister has said and what the PM has said."
He added that the government is ready to discuss the WTO meeting and the question hour should not be disrupted for that.
However, as the members continued to create a ruckus, Rajya Sabha Chairman M. Hamid Ansari adjourned the house till noon.