After dipping below $US100 a tonne last year, the iron ore price rallied in the early weeks of January and could deliver a more than $6.5 billion budget surprise later this year for Treasurer Josh Frydenberg or his successor.

The iron ore price rose 24 per cent in January and topped $US150 a tonne this week before easing slightly; but while elevated, the price is still well below the record $US237 a tonne in May last year.