For months Obama had left the details of healthcare legislation to Congress, then inserted himself firmly into the debate in recent days, including using his weekly radio address to declare that "it's time to deliver" on health reform.
Grassley's first tweet: "Pres Obama you got nerve while u sightseeing in Paris to tell us 'time to deliver' on health care. We still on skedul/even workinWKEND."
A short time later: "Pres Obama while u sightseeing in Paris u said 'time to delivr on healthcare' When you are a 'hammer' u think evrything is NAIL I'm no NAIL."
A Grassley spokeswoman verified that the senator was the author of the messages.
Asked to respond to Grassley's Twitter commentary, White House spokesman Reid Cherlin said: "President Obama is gratified that the Senate is working hard to bring a health reform bill to the floor on schedule. He looks forward to continuing his work with them upon his return from the commemoration of Allied heroism at D-Day."
Grassley's attitude is significant because any hope for bipartisan consensus on healthcare could rest on an alliance between Grassley and Finance Committee Chairman Max Baucus (D-Mont.). The committee has been laboring to come up with a healthcare bill that Democrats and Republicans can support.
Despite strong opposition from most Republicans to one of Obama's key goals for a healthcare bill inclusion of a new government insurance plan to compete with private insurers Baucus and Grassley hold out hope that they can find a bipartisan solution.
Obama senior adviser David Axelrod cited Grassley in an interview on CBS' "Face the Nation" Sunday morning as a reason there's hope for a health overhaul deal.