TRENTON, N.J. (AP) _ Three makers of popular nicotine patches that help people quit smoking have solved chronic supply problems just as a fourth player is elbowing into the market.

Warner-Lambert Co. of Morris Plains, N.J. unveiled its Nicotrol patch Wednesday, joining two other New Jersey companies and one in Missouri battling for the growing pool of smokers trying to quit the high-tech way.

The other competitors are Marion Merrell Dow Inc., of Kansas City, distributor of Nicoderm; Ciba-Geigy's pharmaceuticals division in Summit, N.J, maker of Habitrol; and Lederle Laboratories of Wayne, N.J., maker of ProStep.

Sporadic shortages around the country beginning in February showed patch makers had sharply underestimated demand for their products. The supply problems left many customers unable to refill their prescriptions, and those who didn't go back to cigarettes turned to whatever was patch available.

The companies, some of which farm out production to others, said they boosted supply by increasing the number of shifts and workers. Marion Merrell Dow added new equipment as well.

One analyst estimated the worldwide market for the products is at least $1 billion, or roughly 3 million customers, a year.

''It's going to be much more competitive. There may be some pricing pressure,'' predicted analyst Sven H. Borho with Mehta and Isaly in New York. He said overall sales should increase slightly come fall as the market stabilizes and advertising for the products resumes this month.

The patches cost about $3.50 each and must be changed daily during treatment ranging from six weeks to 20 weeks.

''At the beginning, no customer could develop brand loyalty,'' Borho said.

The brand-shuffling cost Marion Merrell Dow Inc. its number one market position. Ciba-Geigy grabbed the lead and then boosted its market share to 60 percent, Borho estimated Wednesday.

''We were neck-and-neck with Nicoderm'' in February, two months after those two brands went on sale, said Ciba-Geigy spokesman Doug Arbesfeld. ''All of a sudden, they had a really bad shortage and they almost dropped out of the market.''

''It kicked our share up higher than anyone expected,'' Arbesfeld said.

The shift left Marion Merrell Dow with only about 25 percent of sales, and company spokesman Charles Rouse said Wednesday that the last back orders for Nicoderm are only now being filled. Lederle introduced ProStep in February and its market share climbed to about 15 percent.

Because of the shortage, all three companies stopped advertising and started dividing their available product among their customers until they could boost production.

Heavy publicity early on caused the shortages, said Carolyn Fray, spokeswoman for Rite Aid, the nation's largest drug store chain with more than 2,500 stores. She said the problem eased a couple months ago.

''We're in patch heaven now,'' Fray said.

The Thrift Drug chain, with more than 540 stores in 18 states, temporarily kept waiting lists of customers wanting patches, but now has plenty, said spokeswoman Margot Callaghan.

Warner-Lambert later this month will begin widespread distribution of Nicotrol, which is worn 16 hours a day instead of 24 as the other patches are.

Competition is heating up again.

Lederle is offering pharmacists a $2 fee to counsel patrons on its product and gives rebates starting at $50 to customers who fail the first course and try treatment again within 12 months.

Warner-Lambert likely will use ads to stress that its Habitrol is only worn during waking hours, cutting down on adverse effects such as sleeping troubles, Borho said.

All the products offer some type of customer hotline and referral service.

However the market shifts, Borho predicted that Nicoderm won't regain the market lead from Habitrol. But he said Warner-Lambert's new Nicotrol could easily overtake ProStep, despite being the last to enter the market.