Republican mayoral candidate Arthur A. Fletcher said yesterday that large numbers of Democratic voters are offering to support him in the November elections because of their dissatisfaction with the apparent selection of Marion Barry as their party's candidate for mayor.

Among those who are apparently wavering in their traditional support of Democratic Party candidates is the Council of 100 Ministers, which backed Mayor Walter Washington in the primary. The council will make a decision on who it will support by late next week, a spokesman said yesterday.

"I have had a chance to sit down and talk with members of the board of trade, labor leaders and some ministers," said Fletcher. "These people were almost embarrassed to talk with a Republican not long ago. Now, after comparing me to Mr. Barry, they are anxious to hear what I have to say."

The Rev. Andrew J. Allen, pastor of First Baptist Chucrh of Deanwood in Northeast Washington was one of those yesterday who said he intends to support Fletcher for mayor. "I believe Mr. Fletcher has what it takes to lead this city. He has a very constructive program for bringing back businesses and for cleaning up the streets," said Allen.

"Mr. Fletcher is against prostitution and gambling, which Mr. Barry does not oppose," he added. "As I go through the streets talking to people they are really upset with the prospect that Mr. Barry will be mayor. They want someone else and the party.

Fletcher, 53, a former White House assistant who handily defeated Jackson Champion in the Sept. 12 Republican mayoral primary, said attention has focused on him because many voters do not feel Barry is a suitable can-doesn't matter."

"When the voters look at me and then look at Mr. Barry, it's difficult for them to deny that I am by far the better candidate," he said. Board of Trade have pledged to support his campaign in order to generbers of the Metropolitan Washington.

Fletcher also said that some memate "new life" in the Republican Party here.

"They (board of trade supports) believe that a good tough showing by a Republican candidate in November will boost support for full-voting legislation for the District. Legislators across the country will see that a bipartisan attitude is developing in the nation's capital."

Henry Brock, vice president of the Greater Washington Central Labor Council, said yesterday that his organization will not decide on whom it will support until after its members meet with both Barry and Fletcher.

Nevertheless, some of the groups that supported other Democratic candidates in the primary last week are leaning toward backing Barry in the general elections.

Ron Richardson, vice president of the Hotel and Restaurant Employes Union Local 25, said his union, which supported Mayor Washington in the primary, will decide next Tuesday which candidate it will support in November.

"Our inclination now is to vote for Barry," Richardson said. "As far as we're concerned, there is no comparison between the candidates."

Robert B. Washington Jr., chairman of the D.C. Democratic Party, said, "I know there are some unhappy Democrats out there, but there are unhappy Democrats after every election. I supported Mr. Tucker in the primary, but I will support Barry enthusiastically in the general election."

Phil Watson, a knowledgeable observer of city politics who supported Barry's election, said Fletcher does have an appeal to some of the older, middle-class, black church-going and politically moderate-conservative blacks, who, many feel, make up the backbone of the District's electorate.

"They're solid folks who pay their bills on time. They pay their parking tickets," Watson said. "They keep all their crap in the closet. They think what (maverick City Council member) Douglas Moore says, but they would never say it, which is why they're mad at Doug.

"They don't trust Marion and they see sin city coming if he's elected."

Watson said such people were the majority of the voters Sept. 12, but did not have a winning candidate because their votes were split between Washington and Tucker.

Yesterday morning, Fletcher sent Barry a telegram, challenging the apparent Democratic nominee to a series of televised debates.

A spokesperson for Barry said the candidate "has been busy" since last week's primary election and so far has not added Fletcher's offer to debate to the Barry campaign calendar.