UPDATE 2-ArcelorMittal says delays Liberia iron ore mine

* Falling demand for iron ore forces delay

* Jobs lost at company and subcontractor

(Adds job losses, background)

By Patrick Worsnip

MONROVIA, May 20 (Reuters) - The world's biggest steelmaker ArcelorMittal (ISPA.AS: Quote, Profile, Research) has delayed the launch of a planned $1.5 billion iron ore mine in Liberia as a result of falling demand, the company said on Wednesday.

ArcelorMittal, which reported slightly worse than expected first-quarter results in April, has said it expects world steel demand to fall by 15-20 percent this year, and that it will lay off nearly 1,000 workers in the United States.

"If we cannot sell the iron ore it becomes difficult for us to continue on the pace that we thought we would be on by now," company spokesman Arthur Massaquoi said on a conference call with journalists travelling with a United Nations Security Council delegation to the West African country.

ArcelorMittal is a key investor in the poor former British colony, whose President Ellen Johnson-Sirleaf has made attracting foreign investment into its natural resources a centrepiece of her efforts to rebuild the country after a 1989-2003 civil war.