Obama and Putin to come face to face over Syria at the G20
They have issued the threats. They have set out their positions. Today the leaders of the United States and Russia will come face to face.
President Obama flies into Saint Petersburg for a G20 summit at which Syria is both the main and most pressing issue - while also being the issue which isn't officially on any summit agenda anywhere.
As the host, President Putin gets to choose what is debated and what isn't.
Syria will be debated on what is called "the margins" of this summit (the moments the leaders have away from the official summit programme). But all the working sessions will focus in the global economy and tax.
Meanwhile, legislators have been debating controversial air strikes in both Washington and Paris.
In the French capital - there will be no vote.
In the US capital - a vote by Senators on the Committee on Foreign Relations backed a motion for limited strikes without boots on the ground.
A small step forward for the White House.
President Obama will hold talks with his French counterpart when the pair meet at the G20. Perhaps they will share thoughts on how voters in both their countries still need to be persuaded of the legitimacy of the military action.
It's notable and not surprising however that David Cameron will have no formal meeting with the US President.
And that might be something the Prime Minister will have to get used to at this summit.
Last week's decision by MPs to reject Britain's involvement in strikes on Syria will push Mr Cameron to the sidelines of this summit.
Downing Street says he will focus on the diplomatic and humanitarian issues in Syria. But when the rest of the world is focused on the decision to send in missiles, the Prime Minister's role at the G20 will be limited.
This time, all the focus will be on the words and the body language of the leaders who support military action and those who don't.