Yuan ends up; U.S. senators renew probe into peg

* U.S. senators seek probe into yuan "manipulation"

* Dealers expect the yuan may move between 6.8250 and 6.8300

SHANGHAI, Nov 20 - The yuan ended up slightly against the dollar on Friday as the central bank set a stable reference rate, showing its resolve not to allow the yuan to appreciate while two U.S. senators renewed efforts to probe China on its yuan peg.

Expressing frustration over the Obama administration's light touch on China's yuan exchange rate, Senator Charles Schumer, a New York Democrat, and Senator Lindsey Graham, a South Carolina Republican, asked the Commerce Department on Thursday to investigate alleged Chinese currency "manipulation."

The Chinese central bank fixed the yuan's daily mid-point, or reference rate, at 6.8278 versus the dollar, compared with Thursday's level of 6.8274.

Spot yuan rose slightly, closing at 6.8278 on Friday, compared with Thursday's close of 6.8284.

"China faces high international pressure for the yuan to appreciate," said a dealer at an Asian bank in Shanghai. "But now the central bank has no intention of letting the yuan rise. The mid-point point says it all."

Several dealers said they expected the yuan to move between 6.8250 and 6.8300 next week.

Late on Friday, a Reuters poll of 33 respondents showed China's yuan was undervalued by 20 percent, highlighting the case of President Barack Obama who this week pressed Beijing to allow the currency to rise.

"It's a policy issue," said Wensheng Peng, an economist at Barclays Capital in Hong Kong. "In the long term, as the Chinese government wants to promote the yuan as an international currency, that is a driver for liberalisation, but my guess is it will be gradual rather than a big bang."

Offshore, benchmark one-year dollar/yuan non-deliverable forwards (NDFs) rose slightly to 6.6328 bid late on Friday compared with Thursday's close of 6.6300.

Twelve-month yuan appreciation implied by NDFs fell slightly to 2.94 percent measured from the Chinese central bank's daily mid-point, compared with 2.98 percent implied at Thursday's close.