The troubled United Nations Centre for Human Settlements (Habitat), the UN arm dealing with rapid urbanisation, has warned that, if donors do not honour funding pledges this year and increase commitments for 1999, its existence will be at risk.Klaus Toepfer, Habitat's director, said failure to augment pledges of $1m for next year's budget would be "really life-threatening", and called on donors to disburse more than $1m of unpaid commitments for 1998.