An improving job market and expected interest rate increases have been strengthening the value of the dollar, while worries about China's economic growth and a rising oil supply are hurting the price of oil.
The dollar hit a nearly four-month high Friday but slipped a bit in Monday's trading on uncertainty about the timing of an interest rate hike.
The dollar was boosted when the U.S. unemployment rate held steady at its lowest level in nearly seven years, and the economy had a net gain of 215,000 jobs. The improving job market reinforced expectations the U.S. central bank will raise interest rates as early as September.
Higher U.S. interest rates tend to make U.S. investments more profitable, so investors purchase U.S. dollars and equities. Greater demand for dollars and stocks pushes up their prices.
Other reports showed the number of U.S. oil rigs in use rose a bit, at the same time that many investors expect Iran to increase its oil exports.
Reports say China, a major oil consumer, is experiencing a drop in exports, which investors interpreted as a sign of weakening economic growth and lower energy demand.
Oil prices fell below $49 a barrel at one point as oil supplies appeared likely to exceed demand.
Reports in the financial press said China's stock indexes rose Monday, perhaps because investors think disappointing economic data may prompt the government to intervene in the markets to support share prices.
