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U.S. crude strengthens as dollar slips to four-day low

* U.S. oil drilling rig count falls 5 to 858- Baker Hughes

* China-U.S. tensions could drag on oil demand

* Oversupply worries may still weigh on prices (Updates with dollar move, crude increase)

By Jessica Resnick-Ault

NEW YORK, July 20 (Reuters) - Oil prices rose on Friday as a weakening dollar and lower expected August oil exports from Saudi Arabia supported the market, offsetting concerns about U.S.-China trade tensions and supply increases.

U.S. crude strengthened late in the session as the U.S. dollar index slipped to a four-day low, on reports that U.S. President Donald Trump worries that the Federal Reserve will raise rates twice this year.

"The dollar was a one-way ticket for the last couple of weeks and basically reversed directions, giving us some strong support," said Phil Flynn, analyst at Price Futures Group.

The expiring U.S. West Texas Intermediate (WTI) crude for August delivery was up $1.50 cents at $70.96 a barrel by 2:23 p.m. EDT [1823 GMT], while the more liquid September contract rose 14 cents to $68.38 a barrel. U.S. crude is set to end the week little-changed.

Brent crude was up 53 cents at $73.11 a barrel. Brent was on track to fall 2.9 percent in the week.

The expiring U.S. West Texas Intermediate (WTI) crude for August delivery was up $1.50 cents at $70.96 a barrel, while the more liquid September contract rose 14 cents to $68.38 a barrel. U.S. crude is set to end the week little-changed.

U.S. drillers this week cut oil rigs by the most since March, with the rate of growth slowing over the past month with recent declines in crude prices.

Drillers cut five oil rigs for a total of 858 rigs in the week to July 20, according to a weekly report from Baker Hughes (RIG-OL-USA-BHI).

Prices also received a boost after OPEC's largest oil producer, Saudi Arabia, said it would temper its exports next month.

Trade tensions continued to weigh on the market, providing a ceiling for any gains, traders said. Trump said in a CNBC interview he was ready to impose tariffs on all $500 billion of imported goods from China.

Lower oil demand in the United States and China caused by an economic slowdown due to the trade spat between the two countries would likely weigh heavily on markets, some analysts said.

"The impact on world economic growth of a levy of this magnitude will be severe and will likely have a strong negative impact on markets," said Olaf van den Heuvel, chief investment officer at Aegon Asset Management.

The People's Bank of China on Friday reduced its midpoint for the yuan for the seventh straight trading day to the lowest in a year.

The yuan then retreated to a near 13-month low, although it rebounded later.

Signs of Russia and Saudi Arabia increasing oil production, as well as last week's surprise build in U.S. crude stocks, have also weighed on prices, said Tariq Zahir, analyst at Tyche Capital Advisors.

"You're having supply come back on to the markets, so it's not surprising to see a little bit of weakness," Zahir said.

(Additional reporting by Ahmad Ghaddar in London; Aaron Sheldrick in Tokyo; and Andres Guerra Luz in New York; Editing by Dale Hudson, Louise Heavens and Jonathan Oatis)