NEW YORK (Reuters) - AT&T Inc. yesterday posted a higher profit on wireless growth, but a fall in traditional phone users accelerated and some analysts said the top US phone company may yet be hurt by a weaker economy.

Analysts said they were impressed by gains in first-quarter revenue, which rose 6.1 percent from a year earlier to $30.7 billion and came in above an average Wall Street forecast of $30.6 billion, according to Reuters Estimates.

AT&T said quarterly profit rose 21.5 percent to $3.46 billion, or 57 cents per share, from $2.85 billion, or 45 cents a share, in the same quarter a year earlier.

Profit before items, such as merger-related costs and severance charges for recently announced job cuts, totaled 74 cents a share and matched analyst expectations.

"It's pretty impressive to see their revenue growth continue at an increasing rate," said Edward Jones analyst Rick Franklin. "For a very large company it still has growth opportunities."

But Mr. Franklin added that while AT&T managed to grow corporate service revenues and that the popularity of wireless and Internet use was sheltering the company from a US economic downturn, it may be growing more vulnerable.

"They are more defensive than most industries. But then again, while 10 to 15 years ago you had one relationship with the telephone company and that was sacrosanct even in an economic downturn, today you have more than one relationship and it's easier to reduce your relationship," he said.

AT&T shares rose 17 cents, or 0.45 percent, to $37.76 on the New York Stock Exchange.

AT&T, the exclusive US carrier for Apple Inc's iPhone, said it added 1.3 million net wireless subscribers in the quarter, compared with an average estimate of 1.32 million according to seven analysts polled by a Reuters reporter.

Wireless revenue rose 18.3 percent from a year earlier.

Stifel Nicolaus analyst Christopher King said he had expected 1.4 million new subscribers.

He noted that net additions of postpaid users, or those who pay monthly subscriptions instead of prepaid fees, rose by 705,000, just 3.7 percent higher than in the year-ago quarter.

Postpaid subscribers are considered valuable, bringing in more revenue per user. But with 80 percent of consumers already owning phones, and rising unemployment and bankruptcies leading to more consumers with credit problems, analysts say more first-time subscribers may be signing up for pre-paid services.

"We're going to have to see what Verizon says next week. But I'm certainly a little concerned about the wireless side. That number of 705,000 in postpaid is essentially flat year-on-year," Mr. King said.

Both AT&T and rival Verizon Communications Inc. have banked on mobile phones for growth as traditional home phone users decline.

AT&T said primary retail consumer access lines fell 6.2 percent year-on-year, faster than a 4.9 percent decline in the fourth quarter.