KENOSHA, Wis. (AP) _ A man arrested for bilking a woman he dated may be the ''Sweetheart Swindler'' who left broken hearts and depleted bank accounts during a cross- country scam that involved up to 200 women, authorities say.

Investigators say the man identified as Robert J. Koch, 51, used at least 100 aliases and may be involved in fraud cases in 28 states from California to Pennsylvania over the last decade.

''He stays long enough to build up the confidence of the women, wines and dines them, talks about a wedding ring and then it comes time to show up and he's gone,'' Kenosha police Detective Kenneth Kopesky said.

Koch pleaded innocent last week in Kenosha County Circuit Court to charges of theft and forgery. He is accused of bilking a 48-year-old Kenosha woman out of $10,200 during a 10-day romance.

Koch had proposed to the woman and the two went shopping for a wedding ring before the woman gave him money she had drawn from her second-mortgage loan, authorities say.

The woman said Koch appeared sincere and seemed to have a pleasant personality.

''He wouldn't appeal to all women, but if it was the personality that appealed to you, you would think he was very friendly and very outgoing,'' said the woman, speaking on condition of anonymity.

When Koch was arrested March 29 in this southeastern Wisconsin town of 77,000 on the shores of Lake Michigan, he told police he was from Louisville, Ky.

''We thought he was just some guy that was caught trying to rip somebody off, not somebody that was notorious for fraud across the United States,'' Detective Albert Aiello said.

But shortly after the arrest became public the department began receiving calls from other police agencies who reported similar schemes.

Those calls resulted in arrest warrants being issued for Koch in Arlington, Va.; Columbia, Mo., and Kalispell, Mont., and by federal authorities in Dallas. An arrest warrant is also pending in Riverside, Calif.

Other charges may be forthcoming in Michigan, Ohio, Pennsylvania, Nevada and Iowa, Lt. Dennis Conradt said.

Kopsesky said inquiries about Koch also have been made by authorities in Alabama, Arizona, Colorado, the District of Columbia, Florida, Idaho, Illinois, Kentucky, Louisiana, New Jersey, New Mexico, New York, Oregon, South Carolina, Utah, Washington, West Virginia, Wisconsin and Wyoming.

Koch faces trial July 15 in Kenosha. He remains in the County Jail in lieu of $530,000 bail. Conviction on the Wisconsin felony carry a maximum of 20 years in prison and $20,000 in fines.

Soon after he was arrested, Koch scraped his fingerprints off on cement blocks in the jail cell. Police made prints when the skin grew back, but fingerprint checks with the FBI and Canadian authorities failed to verify his true identity.

''Neither we nor anybody else have any idea who he is,'' Lt. Milton Ayers said.

Police said they found 28 identity cards from seven states and Canada when they searched Koch's motel room in March. The aliases - including Dean S. Flowere, Kenneth Luciano, Jesse Cuellar, David R. Coccarelli and Michael Hagepman - made it impossible to determine his true identity, they said.

Police believe Koch traveled between cities by bus, usually staying in one place for two weeks to two months. He would meet women either through ''lonely hearts'' magazine advertisements or through singles' gatherings, police said.

Investigators said he would tell the women he was widowed, wealthy and could take care of their financial needs. He later would propose to marry them before making off with $5,000 to $10,000, police said.

''He had a typical way of operating. ... They trusted him and he took advantage of them,'' said Detective Ralph Ross, a Columbia, Mo., investigator who spent 2 1/2 years on the case of a women was bilked of $3,500 to $5,000.

In a letter dated March 12 police allege Koch wrote to a prospective victim: ''I sure would love to spoil and pamper you in every way ... if you are not married and then we could travel and meet nice people and you would have security for the rest of your life.''

That letter was found in Koch's possession when he was arrested for bilking the Kenosha woman, authorities said.

Koch arrived in Kenosha in February and met the woman on March 17 at a party. He told her he owned an apparel factory in New York, then persuaded her to give him $10,200 to invest in a certificate of deposit, the complaint alleges.

Two friends of the woman, suspicious of Koch's business dealings, hired a private investigator who reported to police that Koch was using a fake name and did not own a New York business, the complaint said.