Environmental groups and the oil industry will square off in their final public showdown on Friday before Barack Obama renders a decision on a controversial pipeline carrying crude from the Alberta tar sands to refineries in Texas.
The encounter promises to be contentious, with one activist Whit Jones (@whitjones) tweeting that the Occupy Wall Street movement had come to the state department.
By 9pm on Thursday night – more than 12 hours before the scheduled start of the public hearing in the basement of the Ronald Reagan trade centre in Washington – about two dozen activists had turned up with sleeping bags determined to camp on site to be the first in the room.
To their frustration, however, industry had a similar plan for the hearing, which was hosted by the state department. Activists said contractors for the TransCanada pipeline company had sent in a professional line-sitter who promptly claimed his spot in line – and then telephoned for reinforcements.
"The industry has done what they can to ensure that their voice is louder than ours at the hearing," said Christine Irvine, an activist with 350.org.
The shows of force on both sides of the fight over the Keystone XL pipeline was due to continue outside the hearing, with activists and industry groups holding competing conferences.
Friday's hearing is the last chance for the public to weigh in on the 1,700-mile pipeline across six states in the American heartland before the state department decides whether to approve it.
Most activists believe that decision is now just a formality; Hillary Clinton has indicated on a number of occasions that she is inclined to support the pipeline. But in the time the state department has been deliberating the political atmosphere has shifted. The pipeline issue is at the top of the environmental agenda.
Environmental activists now argue that if Obama fails to recognise that anger and block the pipeline, he could hurt his chances in the 2012 elections.
In any event, activists say, the fight over the pipeline is far from over.
"This is going to be litigated, this pipeline," said Tony Iallonardo, a spokesman for the National Wildlife Federation. "Even if it is approved, Hillary Clinton or Barack Obama's signature doesn't end the process."
The first of many such lawsuits was filed this week, alleging that government officials had acted improperly in clearing a corridor for the pipeline through northern Nebraska even though the project is still awaiting final approval.
Meanwhile the state department faced a new round of questions about the cozy relationship between government officials and industry lobbyists.
The website DeSmogBlog reported that it had identified seven former aides to Obama and Hillary Clinton who now worked as lobbyists for the pipeline.
Members of the Nebraska state legislature are also exploring legal options – including one proposal which would give the state final authority over pipeline routes.
The proposed pipeline route would cross an important aquifer in Nebraska, and there has been growing pressure on state politicians to get the line rerouted.
The net effect, of the legal challenges and the moves in the Nebraska state legislature, was that TransCanada will almost certainly be forced to delay the project, Iallonardo said.
"I don't think industry is going to have their preferred time line," he said. "They are going to have to deal with the judicial process that we have in the US and they are going to have to defend the decisions that are going to be made in the courts, and I think that probably is going to slow the process beyond their expectations."