Because of a copy editing error, The Washington Post incorrectly reported yesterday that a lobbying effort by mayors for urban aid had started Monday. The mayors' effort in Congress started yesterday.

More than 15 years, worried that most of President Carter's troubled urban program is slipping down the legislative drain, were plumbing the halls of Congress yesterday in an effort to salvage some of it.

"We are deeply concerned that our programs may be caught in a political crossfire between the White House and Congress," said Denver Mayor William H. McNichols Jr., president of the U.S. Conference of Mayors.

The mayors are scheduled to see President Carter tomorrow and plan to call for better lobbying efforts by the administration, which some urban strategists say has been "insensitive to negative feelings on the Hill."

Noting that Congress is pushing towards its summer recess later this month and for an adjournment in early October, McNichols said the mayors fear the lawmakers will not act on programs "which are essential to our cities."

The targets of the mayors' concerns are the supplementary fiscal assistance bill, which would give economically distressed cities $1 billion a year for two years; a measure providing $1 billion a year for three years for public works maintenance jobs on such projects as filling potholes, repairing bridges and fixing up city halls; and a bill to continue the $11 billion Comprehensive Employment and Training Act program.

The CETA bill is scheduled for a vote on the House floor Wednesday. It is not officially a part of Carter's urban program but is considered vital to cities because it would continue 725,000 public service jobs and would provide incentives to industry to hire the long-term umeployed.

The president's 15-part urban program has been in precarious health since he unveiled it in March, but last Tuesday two major sections suffered serious setbacks. One came when the supplementary fiscal aid bill was postponed indefinitely by a 7 to 6 vote of the House intergovernmental relations subcommittee. The other came when the Senate Banking Committee voted 9 to 2 to postpone until 1979 consideration of a bill providing $400 million over two years as an incentive to states that aid troubled cities.

The public works maintenance program is stalled in the House Public Works Committee and some members are said to favor adding $1 billion for regular public works such as building bridges or community facilites. Such a large combination of "soft" and "hard" public works would probably face a presidential veto.

Urban lobbyists, who favor the CETA bill as passed by the House Education and Labor Committee, say that expect opponents to offer amendments on the House floor today that they contend would gut the measure.

Among the expected amendments are those that would reduce the overall authorized spending cut the maximum salaries that CETA job holders could earn, and lower the amount of money cities could contribute to CETA salaries.

The mayors - who are coming from such cities as Boston, San Francisco, New Orleans and Detroit - will meet this afternoon with Sens. Edmund S. Muskie and William D. Hathaway, both Maine Democrats, and with House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) and House Majority Leader James C. Wright Jr. (D-Tex.)

One urban lobbyist said yesterday, "We have indications the congressional leadership wants to do something to reverse the urban aid losses."

On the supplementary fiscal aid bill, the lobbyist said, the suggested strategy will be to try to persuade the Senate Finance Committee to add it as an amendment to a House-passed bill, get approval of the amended measure on the Senate floor and then try to win support in a conference with members of the House Ways and Means Committee.