"But China's still growing, and that continues to be an underlying support factor long term for the market. Whether they are at 6 percent or 7 percent, they are growing."
Data showing the pace of expansion in the U.S. manufacturing sector slowed in March and weaker equities on Wall Street also weighed on U.S. oil prices on Monday.
This week will see several key economic reports, including euro zone unemployment data due on Tuesday and U.S. March nonfarm payrolls data due on Friday.
Oil investors are also monitoring upcoming negotiations between Iran and the U.N Security Council members, plus Germany, over Tehran's disputed nuclear program.
The United States and European Union have sanctioned Iran's oil exports in a bid to force concessions from Tehran. (Additional reporting by David Sheppard in New York, Dmitry Zhdannikov in London and Luke Pachymuthu in Singapore; Editing by Peter Galloway)