LONDON (AFP) - Crude oil prices were narrowly mixed on Tuesday, with sentiment muted amid a budget standoff in Washington over a plan to avoid a debt default. New Yorks main contract, light sweet crude for delivery in September, advanced by just 14 cents to $99.34 a barrel. Brent North Sea crude for September eased seven cents to $117.87 in London deals. Investors (are) keeping to the sidelines as Washington debates the debt ceiling, analysts from Phillip Futures said in a commentary. The United States is meanwhile the worlds biggest consumer of oil. The US treasury says Congress must raise the governments $14.29 trillion debt limit by August 2 to prevent a default, which would have devastating repercussions on the global economy. But Democrats and Republicans are deadlocked, with bitter disagreements over tax increases and spending cuts.