The number of Americans filing new claims for state unemployment insurance dropped below 600,000 for the first time in three months during the week ending Nov. 13, the Bureau of Labor Statistics reported yesterday.

Although the decline--the fourth consecutive weekly drop--was welcomed, administration officials pointed out that the latest figures may have been artificially lowered because of the Veterans Day holiday that week. State unemployment offices, where the jobless claims are placed, were open for only four days that week.

New jobless claims in the week ending Nov. 13 totaled 599,000 after seasonal adjustment.

Some analysts believe that recent declines in unemployment insurance claims, from a high of 703,000 in the week ending Sept. 18, are a sign that the unemployment picture is beginning to improve. "Hurray," commented economist Otto Eckstein of Data Resources Inc., on hearing yesterday's figures.

These show "there is some hiring going on," he said. The overall unemployment rate, which reached 10.4 percent in October, "ought to be down in November," he said. "It certainly should be dropping in November or December."

On the basis of fragmentary data now available, DRI currently believes there could be an upturn in production in November, Eckstein added. Economic indicators released recently show the economy was still sinking last month, long after many forecasters had expected a recovery to begin. New orders for durable goods manufacturers dropped sharply in October, a report from the Commerce Department said this week.

The jobless claims in the week ending Nov. 6 were revised to be 628,000, down slightly from the 629,000 first reported, the BLS said. The last time the claims were as low as in the latest week was in the week ending Aug. 7, when they totaled 566,000.

The rate of insured unemployment was unchanged in the latest week at 4.4 percent, yesterday's Labor report said. The number of people claiming unemployment insurance benefits was 3,824,700, down 67,300 from the previous week, it said.

Administration officials, who expect only a moderately paced recovery next year, have said that unemployment will likely stay above 9 percent next year. The jobless rate is now at its highest level since before World War II.