* USDA biannual cattle data due at 2 p.m. CST (2000 GMT * Futures' premium to cash, fallen beef prices weigh * Feeders weaken by live cattle, pre-report caution * Feb hogs gain on discount to cash, others lower * Russia meat ban hangs over livestock markets By Theopolis Waters CHICAGO, Feb 1 (Reuters) - Chicago Mercantile Exchange live cattle futures closed lower on Friday amid caution before the government's biannual cattle inventory report at 2 p.m. CST (2000 GMT), analysts and traders said. Analysts expect the report to show the U.S. cattle herd declined for a sixth straight year as drought drove up feed costs. Also, futures' premium to cash cattle prices and pushback by grocers and other buyers against beef at higher prices prompted selling. And traders cited market uncertainty as Russia announced plans to ban imports of U.S. beef and pork, effective Feb. 11. CME spot February live cattle closed at 127.100 cents per lb, 0.525 cents lower. April ended down 0.625 cent at 132.175 cents. Live cattle futures finished up 0.67 percent for the week. Cash-basis cattle in the U.S. Plains traded at $125 per cwt, compared with $122 to $125 last week, feedlot sources said. Packers raised bids for cattle due to fewer animals available than a week ago and tighter supplies ahead. But elusive margins and slumping wholesale beef prices limited how much processors were willing to spend for supplies. Tyson Foods executives could not confirm talk in the CME live cattle market that the potential shortage of cattle would prompt the company to scale back slaughter operations at all of its beef plants. The price for wholesale choice beef Friday morning was $183.99 per cwt, down $1.33 from Thursday, and select cuts dropped 69 cents to $179.56, according to the USDA. HedgersEdge.com put the average beef packer margin for Friday at a negative $48.10 per head, compared with a negative $26.25 on Thursday and a negative $45.45 on Jan. 25. CME feeder cattle closed lower, weakened by live cattle losses and pre-report caution. Futures closed 3.1 percent higher for the week. March finished down 0.350 cent per lb at 149.200 cents and April closed 0.450 cent lower at 152.125 cents. MOST HOGS SLIDE Spot February hog futures drew support from its discount to CME's lean hog index at 88.25 cents, while other months wilted on profit-taking. CME hogs closed up 0.89 percent for the week. Spot February hogs settled up 0.050 cents per lb to 87.650 cents. Most-active April ended at 88.750 cents, 0.750 cents lower, and June closed 0.600 cent lower at 97.500 cents. "People couldn't get a firm handle on cash prices, and packers' margins are getting away from them. Also, folks are starting to get a little antsy about that Russian meat import issue," a trader said. The average hog price in the most-watched Iowa/Minnesota market Friday morning was $3.04 per cwt lower at $86.49 per cwt in extremely light volume after being up $2.05 on Thursday, USDA said. The average pork packer margin for Friday was a negative $10.15 per head, compared with a negative $5.20 on Thursday and a negative $8.65 on Jan. 25, according to HedgersEdge.com.