(Reuters) - The U.S. dollar hit its highest in over a month against the euro and yen on Tuesday, buoyed by its safe-haven status on uncertainty about whether the United States will eventually conduct a military strike against Syria. While U.S. President Barack Obama opted to seek congressional authorization for military action against Syria, a move that was likely to delay any strike for at least several days, geopolitical concerns are keeping investors cautious. Israel tested a U.S.-backed missile system in the Mediterranean on Tuesday but did not announce the launch in advance, prompting a disclosure by Russia that kept the world on edge as the United States weighed an attack on Syria. Congress returns from its summer recess on September 9, and any vote to authorize a strike will come after that. While Obama has been pushing Congress to back his plan, passage is by no means certain, easing some concerns over an imminent strike. The safe-haven yen rose on a media report that Russian radar detected two ballistic 'objects' that were fired towards the eastern Mediterranean. But it gave up those gains after investors realized it was not a missile strike. "The reaction does speak volumes about the nervousness of the markets as traders await the escalation of conflict with trepidation," said Boris Schlossberg, managing director of foreign exchange strategy at BK Asset Management in New York. "Although President Obama has stressed the limited aspect of any engagement in Syria, the markets continue to be concerned about any possible fallout from the U.S. military action that could precipitate and the market will therefore remain jittery for the near term." The dollar regained poise, helped by a rise in U.S. Treasury yields. The interest rate-sensitive 2-year Treasury note yield traded at the highest since July 2011. Investors are betting the Federal Reserve may start withdrawing stimulus, perhaps as early as this month, especially if the U.S. jobs market shows more signs of improvement. U.S. manufacturing activity, meanwhile, eased in August as output grew at the slowest pace in 10 months, but demand picked up and inventories fell, suggesting growth may soon speed up. The euro fell against the dollar, weighed by expectations that the European Central Bank this week will reiterate its pledge to keep interest rates low to support a nascent recovery. The euro fell to $1.3157, its lowest level since July 22 and was last trading 0.1 percent lower on the day at $1.3180. Its weakness saw the dollar index .DXY gain 0.25 percent to 82.281, near its highest level in a month. "Investors do not want to be long euros heading into the ECB meeting this Thursday," said Geoffrey Yu, currency strategist at UBS. "We haven't heard for a while from (President Mario) Draghi. We expect him to say conditions remain soft despite an improvement in the data and pledge to keep rates low." Reflecting investor nervousness, one-month euro/dollar implied volatility, a gauge of expected price swings and derived from option prices, has risen to 1-1/2 month highs of around 8.6 percent. The one-month risk reversals are also showing an increasing bias for euro puts/dollar calls, or bets the single currency will weaken. The risk reversals were trading 1.3 vols in favor of euro puts, up from around 1 just a week ago. While the ECB is expected to keep monetary policy loose, traders expect the Fed to start reducing stimulus at its policy meeting on September 17-18, unless U.S. payroll numbers due on Friday disappoint in a big way. On Tuesday, the focus will be on the August ISM manufacturing PMI survey. The dollar rose as high as 99.70 yen, near its August 2 peak of 99.94 yen, after having gained more than 1 percent on Monday. It was last trading up 0.2 percent at 99.48 yen, recovering from a low of 99.14 yen struck after the reports from the Mediterranean. (Additional reporting by Anirban Nag in London; Editing by Chris Reese)

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