Oct. 21 (Bloomberg) -- OPEC, whose members will meet this week to discuss oil production levels, will be pushed to reduce output by between 2 million and 2.5 million barrels a day if demand declines 8 percent to 10 percent, Iran said today.

``The decrease in the value of oil over the long term will harm producers because it reduces their motivation to invest,'' Oil Minister Gholamhossein Nozari said at a conference in Tehran.

The Organization of Petroleum Exporting Countries, which supplies more than 40 percent of the world's crude, is due to meet Oct. 24 in Vienna. Oil has tumbled more than 50 percent since reaching a record $147.27 a barrel in July.

Nozari and his Qatari counterpart Abdullah bin Hamad al- Attiyah met with Alexei Miller, chief executive officer of Russian gas exporter OAO Gazprom, in Tehran today to discuss joint gas exploration and production.

``We don't expect oil prices of $100 a barrel,'' al-Attiyah said in an interview at the conference. ``That is over now. $80 to $90 is a suitable price.''

Oil-producing nations have the right to safeguard their economies, just like the U.S. and U.K., al-Attiyah said. ``We don't want our economies to be in a mess.''

To contact the reporters on this story: Ladane Nasseri in Tehran at lnasseri@bloomberg.net; Shaji Mathew in Dubai at shajimathew@bloomberg.net

Last Updated: October 21, 2008 05:06 EDT