G20 members are bracing for the US potentially taking a hardline going into the final communique, a formal joint statement that leaders collectively put out after the summit.

According to a source familiar with the discussions, National Security Advisor John Bolton is pushing an "either accept all of our language, or we're not in it" stance.

The language that Bolton currently wants makes no mention of free trade without fair trade, no bolstering of international trade institutions, no mention of the Paris climate deal, and no connection between emissions and climate change, the source said.

A White House official said Friday morning that the US "is committed to working toward consensus on the communique but will stand firm against language that prejudices US positions and is willing to walk away if necessary."

The official adds the US is leaving some room for compromise, but has made clear that there are certain positions regarding the communique that are non-negotiable -- at least, "not right now."

Here's the caveat, given Trump's unpredictable mood -- that in the end he may well go along with the G20 group.

The source added that Trump doesn't like to be the odd man out, which is why he joined the G7 communique this June (before then pulling out after a Twitter spat with the Canadians).