SHANGHAI, April 19 (Reuters) - China"s yuan eased marginally against the dollar on Monday, as some investors shifted their attention to a potential flare-up in tensions between Beijing and Washington, but losses were pared by signs of tightness in onshore money markets. Prior to market opening, the People"s Bank of China (PBOC) set the midpoint rate at a near four-week high of 6.5233 per dollar, firmer than the previous fix of 6.5288. In the spot market, onshore yuan opened at 6.5282 per dollar and was changing hands at 6.5258 at midday, 46 pips weaker than the previous late session close. Currency traders said the yuan continued trading sideways on Monday, with many investors becoming cautious ahead of a U.S. Senate panel"s consideration of a China bill to gauge future developments in Sino-U.S. relations, a critical factor weighing on the yuan over the past few years. "Market will continue to watch out for the collaboration between U.S. and China on climate change after a fruitful discussion between top climate officials in Shanghai last week," Tommy Xie, head of Greater China research at OCBC Bank in Singapore, said in a note. "However, the U.S.-China relationship is likely to be clouded by the upcoming bipartisan "Strategic Competition Act of 2021"." The Senate Foreign Relations Committee is scheduled to vote on a 280-page bipartisan bill that aims to counter China"s influence on April 21. Some analysts and economists pointed out that the Biden administration, unlikely its predecessor, has shifted its China focus away from trade imbalances. "Without the return of trade war, the escalating China-U.S. tensions should prove to (be) less destructive to the RMB but the increasing financial sanctions, if any, could disrupt capital flow to China and fuel RMB volatility," said Ken Cheung, chief Asian FX strategist at Mizuho Bank in Hong Kong. The domestic currency market largely ignored the U.S. Treasury Department"s decision not to label China as a currency manipulator in the first semi-annual foreign exchange report issued by Treasury Secretary Janet Yellen. Losses in the local currency were capped by slightly tighter liquidity conditions in the onshore interbank market as tax season approached. The interest rate on China"s benchmark overnight repo traded in the interbank money market jumped to 2.31% in the morning session, the highest level since April 1. The global dollar index rose to 91.651 at midday, while the offshore yuan was trading at 6.5257 per dollar. The yuan market at 0405 GMT: ONSHORE SPOT: Item Current Previous Change PBOC midpoint 6.5233 6.5288 0.08% Spot yuan 6.5258 6.5212 -0.07% Divergence from 0.04% midpoint* Spot change YTD 0.04% Spot change since 2005 26.83% revaluation Key indexes: Item Current Previous Change Thomson 96.42 96.46 0.0 Reuters/HKEX CNH index Dollar index 91.651 91.618 0.0 *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 6.5257 0.00% * Offshore 6.7054 -2.72% 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 Winni Zhou and Andrew Galbraith; Editing by Stephen Coates)