A Reuters survey showed on Tuesday that OPEC increased production in July.
OPEC hiked production by 70,000 barrels per day to 32.64 million bpd, a 2018 high, Reuters reported. Further supply increases could offset production outages and pressure prices, it added.
Oil prices received some support on Monday as investor concerns over global crude supply supported sentiment, as investors continued to weigh supply disruptions in Saudi Arabia and declining output from and Venezuela, Iran and Libya.
Saudi Arabia announced it would suspend shipments of oil through the key Bab el-Mandeb Strait, after Houthi rebels in Yemen attacked a pair of oil tankers in the Red Sea.
Combined flows from Iran, Libya and Venezuela fell to their lowest since January, JBC Energy said.
Meanwhile, the U.S. Dollar Index, which tracks the greenback against a basket of other currencies, fell 0.01% to 94.13 on Tuesday, off a one-year high of 95.656 touched on July 19.
Dollar-denominated commodities such as oil are sensitive to moves in the dollar. A fall in the dollar makes oil cheaper for holders of foreign currency, raising demand.