The benchmark U.S. oil price tumbled to a six-week low Friday, thwarting hopes for a sustained recovery after an influential energy watchdog said U.S. production growth is defying expectations and setting the stage for another bout of price weakness. Investors and oil producers should brace for further declines in oil prices , the International Energy Agency said in a monthly report. Prices haven’t fallen far enough yet to cut supply, and some signs of rising demand are just temporary—bargain buyers using cheap oil to fill up stockpiles, the agency said. That outlook weighed on sentiment in the oil-futures market, which has stabilized in recent weeks following a seven-month selloff that saw the benchmark price on the New York Mercantile Exchange plunge 59%. Behind the selloff, which by some measures was the steepest in decades, was a global glut of crude spurred by rising production in the U.S. and Libya. […]