* Credit use surges but reasons aren't clear
* Analysts say could be confidence or even desperation
* Car sales, production pushing expansion
WASHINGTON, May 7 (Reuters) - U.S. consumers went back to using their credit cards in March to keep spending while student and new-car loans shot up as the value of outstanding consumer credit jumped at the fastest rate since late 2001, data from the Federal Reserve showed on Monday.
Total consumer credit grew by $21.36 billion - more than twice the $9.8 billion rise that Wall Street economists surveyed by Reuters had forecast. That followed a revised $9.27 billion increase in outstanding credit in February.
Analysts expressed some reservations whether the data reliably signaled a real pickup in demand, something that would normally fuel stronger growth, or just a need to rely more on credit in an economy generating anemic job growth.
"The optimistic read is that consumers' improved outlook on the economy and employment prospects led them to feel comfortable spending on credit, while a more downbeat interpretation is that credit is needed for consumers to keep up," Nomura Global Economics said in a note afterward.
The March rise in consumer credit was the strongest for any month since November 2001 when it soared by $28 billion. That was shortly after the September 11, 2001 attacks when big automakers were offering zero-percent financing and other incentives to lure consumers back to their showrooms.
New-car sales and production were a key influence on the 2.2 percent annual rate of economic growth posted during the first three months this year. The government estimated that about half of that growth came from increased new car production.
The March figures showed consumers once again expanding their credit card use after two months in which they had paid this debt. So-called revolving, or credit-card, debt rose $5.18 billion after declining by $2.35 billion in February and $2.95 billion in January.
Paul Edelstein, an economist with IHS Global Insight in Lexington, Massachusetts, said it might mean that consumers have now paid down debt that they accumulated over the holiday season and were ready and able to take on more, but cautioned that was not a certainty.
"The bearish view is that with income growth anemic, households needed to use their credit cards to pay for higher gasoline prices in March," he added.
The main increase in March consumer credit was concentrated in nonrevolving credit, a category that includes student and car loans. It climbed by $16.17 billion following a revised $11.62-billion gain in February.
Concern about student loan levels has increased in an environment where newly graduating students face difficulty finding a job and keeping up with loan payments.
Congress is currently considering how to prevent a low interest rate for student loans from doubling on July 1 and is expected to find a way to do so, if only to avoid irritating young voters ahead of November's presidential elections.
A scarcity of job opportunities has led more people to seek retraining at colleges and universities which has also contributed to loan demand and growth in outstanding credit.
"We expect that student loan growth will continue to push the level of consumer credit outstanding higher, and we look for revolving credit to expand as banks become more willing to lend," Barclays Bank PLC said in a statement.
Last week, the Fed said in its latest report on bank lending standards that bankers had become more willing to lend and that demand for business loans had increased in the first three months of this year.
That was taken as a hopeful sign for expansion because credit standards had tightened sharply after the 2007-09 recession and any loosening of standards could indicate an easier flow of credit that is vital to fuel growth.