Oil prices slipped on Monday, but held near recent three-month highs amid optimism that the United States and China are close to signing a trade deal, with President Donald Trump saying an agreement would be signed “very shortly”.”Oil prices will continue to benefit from the positive developments in the U.S.-China trade,” said Stephen Innes, chief Asia market strategist at AxiTrader. The easing of tensions has improved business confidence and boosted the outlook for economic growth and energy demand.The United States is to agree to reduce some tariffs in return for a big increase in purchases by Chinese importers of American farm products, according to the deal that is due to be signed in January Drillers added 18 oil rigs in the week to Dec. 20, bringing the total to 685, the most since November, Baker Hughes, an energy services company, said in its weekly report.