The yearly battle over the US budget officially begins on February 2, when the president plans to send his fiscal 2016 funding proposal to Congress, where it will be torn to shreds or ignored entirely.

While the annual drama involves trillions of dollars, it's usually of limited interest to far-flung governments around the world. Not this year, though, thanks to a budget line item whose fate will be closely tracked by an international audience.

US President Barack Obama faces a budget battle over climate fund. Credit:AP

The line item of interest is President Barack Obama's expected request for money for the Green Climate Fund, which is a key component in the push for a global agreement this year to limit global warming. The fund is meant to collect and distribute money from developed nations to help poorer and developing countries lower future carbon emissions and prevent further damage from the effects of climate change.

It's unclear how much GCF money will be included in the upcoming budget, but Obama pledged to provide $US3 billion ($3.65 billion) over the next four years. Whatever the amount, it will be under attack from congressional Republicans who question the science behind climate change and have vowed to block any related funding, including Obama's pledge to the GCF.