"Thirty percent of the increase (in the price) of oil is because of the decrease in the value of the dollar," he said on the sidelines of the South Asia Association for Regional Cooperation (SAARC) summit in the Sri Lankan capital Colombo.
He did not say what time period he was referring to. The dollar has dropped 33.8 percent against a basket of six currencies since U.S. President George W. Bush took office on January 20, 2001, according to the New York Board of Trade's dollar index .DXY.
Oil has seen a heavy selloff since hitting a record high above $147 on July 11, but U.S. crude futures ended higher on Friday on concerns about Nigerian supply snags and the West's dispute with Tehran over Iran's nuclear programme.
The West suspects Iran is pursuing nuclear technology in order to build weapons, a charge Iran denies. On Saturday its President Mahmoud Ahmadinejad said the country would not retreat "one iota" from its nuclear rights.
His comments were an apparent rebuff to Western powers who had set Saturday as an informal deadline for Iran to respond to their offer to hold off from imposing more U.N. sanctions on Iran if it froze any expansion of its nuclear work.
Mottaki also said unspecified behind-the-scenes actions had played a role in the oil price increase, and that Iran supported "the stability of the oil price in the market".
(Reporting by Shihar Aneez; writing by Jon Boyle; Editing by Kevin Liffey)
