It's fascinating that Republican House Speaker John Boehner's first act since the State of the Union is to invite Israeli Prime Minister Benjamin Netanyahu to address Congress on the subject of Iran's nuclear ambitions.
He doesn't trust Iran, and believes the West is about to make an historic mistake in trusting Tehran to show good faith on the country's nuclear ambitions.
Last night Barack Obama was arguing that negotiations were at a delicate stage with Tehran over a deal.
A deal that would be jeopardised, he believes, by Congress voting for tougher sanctions against Iran at this stage.
It's also the subject that British Prime Minister David Cameron got involved in when he was meeting the president in Washington last week - he phoned a number of Senators (which I understand Obama's closest advisors were delighted about) to argue that tougher sanctions would destabilise the talks.
On this bit of foreign policy it is clear there is profound mistrust between Congress and the White House - and the decision to invite Mr Netanyahu - a man who has the most testy relationship with the president - must be seen as a poke in the eye to Barack Obama.