Credit: NASA/JPL-CALTECH

A further budget overrun for NASA's Mars Science Laboratory rover (pictured), due to launch in 2011, could for the first time delay other missions in the agency's cash-strapped planetary-science division.

In a report due to be handed to Congress by the end of July, NASA will announce that the mission needs between $15 million and $115 million more than its estimated price tag — which, at $2.28 billion, is already 40% above an official $1.63-billion estimate made in 2006.

The agency has so far raided technology-development funds within the Mars programme, but if additional costs rise too much, it may have to delay two planned Moon missions. "The time for some tough decisions is here," said NASA science chief Ed Weiler, breaking the news to planetary scientists at an advisory-committee meeting on 9 July at NASA headquarters in Washington DC. Weiler also confirmed, as expected, that NASA would work in partnership with the European Space Agency on all future major Mars missions.