I'm in Barcelona, Spain for the last round of climate negotiations prior to the big show set for mid-December in Copenhagen. I just touched down, so pardon any poor grammar, I'm a little bleary eyed at the moment.

The goal of the Barcelona meeting is to whittle down the final document that will be presented to leaders at the Copenhagen international climate summit. This document will ultimately become an international treaty that will be the road map for worldwide greenhouse gas emission cuts over the coming decade.

The Barcelona meeting is also a time for political brinkmanship between nations to begin. First out the gate this morning was Yvo de Boer, the man in charge of the entire United Nations treaty negotiation process, who had choice words for the United States.

"We need a clear target from the United States in Copenhagen," said de Boer. "That is an essential component of the puzzle."

De Boer's words were chosen carefully, as most are in such negotiations. By singling out the United States he is setting the tone for the week.

This isn't surprising given that it is still unclear what the US is willing to commit to - either domestically with their clean energy bill currently making its way through the US Senate, or internationally with the US negotiating team continuing to waffle on the important issues of financial support for developing nations, and a hard cap on greenhouse gas emissions.

Lofty rhetoric and no details is the name of the game for the US negotiating team.

You can't blame the US negotiators here in Barcelona though, they are only the government servants acting on the wishes of their political masters. Their most imposing master being the US Congress. As de Boer pointed out today in his press conference, there is no sense in the US committing to a climate deal that is unacceptable to Congress. This will only result in another Kyoto Protocol-like situation where the US signs  a deal on the world stage only to have it vetoed back home.

To add a further twist, there's really no point in world leaders signing a treaty that does meet the greenhouse gas emission targets that scientists are telling us we need to meet, which is somewhere in the neighborhood of a 40% reduction by 2020 based on 1990 levels. There's been no indication to this point that the US is willing to do this.

I'll hold my breath a little longer in the hopes of seeing the framework for a strong deal to come out of the negotiations here in Barcelona this week. But historically there's only one thing Congress dislikes more than science and that's international treaties.