Vice President Mike Pence told President Trump on Tuesday that he did not believe he had the power to block congressional certification of Joseph R. Biden Jr.’s victory in the presidential election despite Mr. Trump’s baseless insistence that he did, people briefed on the conversation said.

Mr. Pence’s message, delivered during his weekly lunch with the president, came hours after Mr. Trump further turned up the public pressure on the vice president to do his bidding when Congress convenes Wednesday in a joint session to ratify Mr. Biden’s Electoral College win…

Even as he sought to make clear that he does not have the power Mr. Trump seems to think he has, Mr. Pence also indicated to the president that he would keep studying the issue up until the final hours before the joint session of Congress begins at 1 p.m. Wednesday, according to the people briefed on their conversation.

One option being considered, according to a person close to Mr. Trump, was having Mr. Pence acknowledge the president’s claims about election fraud in some form during one or more of the Senate debates about the results from particular states before the certification. Mr. Pence will preside over those debates.