The White House has rejected a new plan by Republican House leaders in the US to avoid a disastrous debt default, calling it a "ransom" demand.

The partial government shutdown is already in a 3rd week with many workers laid off. America must raise its borrowing limit by Thursday or risk defaulting.

The latest difficulties emerged after a meeting of House Republicans this morning. They say the package emerging from the Senate does not meet their minimum demands.

Reports say they have tabled their own, with new conditions attached.

House speaker John Boehner says he will not let a debt default happen.