* Syria conflict continues to haunt market * U.N. investigators finish gathering samples in Syria * U.S. makes case for limited military action * Weak U.S. consumer spending muddles Fed outlook * Speculators raise bets in favor of the dollar By Julie Haviv NEW YORK, Aug 30 (Reuters) - The U.S. dollar rose to a four-week high against a basket of major currencies on Friday, ending the month with its strongest gain since May, as the possibility of a U.S. military strike on Syria had investors shunning risk. The United States made clear on Friday that it would punish Syrian President Bashar al-Assad for the "brutal and flagrant" chemical weapons attack that it says killed more than 1,400 people in Damascus last week. U.S. Secretary of State John Kerry made a broad case for limited U.S. military action against Syria for its alleged use of chemical weapons, saying it could not go unpunished for such a "crime against humanity." "Today's combination of risk aversion (on Syria) and expectations of Fed tapering next month suggest we will have continued dollar strength next week," said Camilla Sutton, chief currency strategist at Scotiabank in Toronto. "Next week should be quiet leading up to Friday's nonfarm payrolls report, but the technicals and fundamentals suggest we have entered a new period of U.S. dollar strength," she said. Worries about a Syrian conflict pushed the dollar index, which tracks the greenback against a basket of six major currencies, to a four-week high of 82.263. The dollar index, which last traded up 0.2 percent at 82.078 , was also buoyed by weakness in the euro, the largest component of the index, which fell on soft data out of the region. A team of U.N. investigators has finished gathering samples and evidence in Syria related to a suspected chemical weapons attack that killed hundreds of people in suburbs near Damascus last week and is packing up to leave, a U.N. spokesman said on Friday. A U.S. intelligence report disclosed that there was "high confidence" that Syrian forces had used chemical weapons multiple times in the last year, including the Aug. 21 attack outside Damascus. The dollar index was up 0.9 percent on the week, its third straight weekly gain. After falling for two straight months, the dollar index gained 0.8 percent in August, its best gain since May. Currency speculators, meanwhile, increased their bets in favor of the U.S. dollar in the latest week, according to data from the Commodity Futures Trading Commission released on Friday, snapping five straight weeks of declines. The value of the dollar's net long position rose to $15.82 billion in the week ended Aug. 27 from $13.54 billion the previous week. Looking ahead, next Friday's nonfarm payrolls report should be the highlight of the week since the state of the jobs market is key to Federal Reserve policy. A strong number should affirm expectations that the Fed will pull back on its monetary stimulus when it meets later in the month. U.S. financial markets will be closed on Monday in observance of the U.S. Labor Day holiday. Friday's U.S. data were soft, save for the manufacturing index for the Midwest, which saw the index for prices paid, an inflation signal, rise to its highest since November. But the 0.1 percent increase in both personal income and consumption was lower than expected for the month of July. many market participants, however, believe those numbers won't prevent the Federal Reserve from paring back its stimulus next month, even if the reduction is at a smaller scale. The euro was down 0.2 percent at $1.3214 after earlier touching a five-week low of $1.3172. The currency slipped from highs after data showed benign inflation and elevated unemployment at 12.1 percent. Investors will be wary of buying the euro before next week's European Central Bank interest rate meeting, where policymakers are likely to reiterate their pledge that rates will be low for some time as economic recovery sets in slowly. "Euro zone unemployment shows that the real economy is in dire straits and underlines that the ECB must keep monetary policy super-accommodative for years to come," said David Brown, economist at New View Economics. The dollar fell 0.2 percent to 98.14 yen, according to Reuters data.