SHANGHAI, Dec 10 (Reuters) - China"s yuan weakened to a one-week low against the dollar on Thursday as increasing political uncertainties over U.S. stimulus talks and Brexit negotiations aided safe-haven support for the greenback. Despite rising short-term yuan volatility, many economists remain bullish on the currency, citing continuous foreign inflows and China"s strong economic recovery. In the onshore market, the spot yuan was changing hands at 6.5430 at midday, having touched 6.5527, the weakest level since Dec. 3. The People"s Bank of China set the midpoint rate at 6.5476 per dollar prior to market open, the lowest since Dec. 4. "Participants appeared to be less bullish on the RMB outlook in the near-term," wrote Ken Cheung, strategist at Mizuho Bank Ltd. The choppy performance "reflected the solid USD buying demand from banks and corporates at 6.50 handle by year-end." The dollar index, which tracks a basket of major currencies, rebounded to nearly 91 on Thursday, from a low of 90.47 a week ago. Uncertainly over U.S. stimulus and Brexit weighed on global investor sentiment, increasing dollar demand, Keung said. However, Lu Ting, China economist at Nomura, expects the yuan to strengthen further to 6.25 against the greenback by the end of 2021, saying a strong yuan helps attract foreign capital, discouraging supply chain migration. China"s exports jumped 21.1% in November, the fastest pace in almost three years, despite the yuan"s strong gain that month. "In light of strong China exports figure, the PBoC should have a higher tolerance to allow more RMB strength but the one-way RMB appreciation expectation is probably not to be encouraged," Cheung wrote. The Thomson Reuters/HKEX Global CNH index, which tracks the offshore yuan against a basket of currencies on a daily basis, stood at 95.39, weaker than the previous day"s 95.6. The offshore yuan was trading at 6.5268 per dollar. The yuan market at 4:39AM GMT: ONSHORE SPOT: Item Current Previous Change PBOC midpoint 6.5476 6.5311 -0.25% Spot yuan 6.5413 6.545 0.06% Divergence from -0.10% midpoint* Spot change YTD 6.45% Spot change since 2005 26.53% revaluation Key indexes: Item Current Previous Change Thomson 95.39 95.6 -0.2 Reuters/HKEX CNH index Dollar index 90.994 91.096 -0.1 *Divergence of the dollar/yuan exchange rate. Negative number indicates that spot yuan is trading stronger than the midpoint. The People"s Bank of China (PBOC) allows the exchange rate to rise or fall 2% from official midpoint rate it sets each morning. OFFSHORE CNH MARKET Instrument Current Difference from onshore Offshore spot yuan 6.5268 0.22% * Offshore 6.6763 -1.93% non-deliverable forwards ** *Premium for offshore spot over onshore **Figure reflects difference from PBOC"s official midpoint, since non-deliverable forwards are settled against the midpoint. . (Reporting by Samuel Shen and Andrew Galbraith; Editing by Sam Holmes)