Saying he is particularly concerned about youth unemployment that is as high as 40 per cent in some areas, President Carter yesterday urged Congress to pass five new or expanded programs aimed at creating 243,000 new jobs for youth.

One of the programs, a "National Youth Conservation Corps," is a year-round expansion of the present summer youth conservation corps, and is similar to a proposal that passed the House, but not the Senate, last May.

Carter said the $1.5 billion cost of the "youth employment pckage" is already included in the economic stimulus package he sent to Congress Jan. 27.

Carter announced the youth programs at the start of his third televised news conference, and filled in some of their details in a special message he sent to Congress yesterday.

In that message, he said there are 900,000 full-time and 1,135,000 summer jobs for youth in existing programs. He urged three new programs that, he said, "we can begin under current legislative authority but for which we seek a specific legislative mandate." They are:

$350 million over 18 months to create 35,000 jobs in a National Youth Conservation Corps, employing persons aged 16-24 to conserve and maintain public parks, forests and recreation areas.

$250 million over 18 months to create 30,000 jobs in "Youth Community Conservation and Improvement Projects," employing youths aged 16-19 to improve urban neighborhoods and rural communities.

$900 million to create 138,000 new CETA (Comprehensive Employment and Training Act) jobs for disadvantaged or low-income youths aged 16-21. Half of this money would be "used by the Secretary of Labor to encourage innovative and experimental programs."

As with current CETA programs, Carter said, private community groups as well as local government agencies would be eligible for grants to run the new CETA programs.

In addition, he urged a one-year extension of CETA, which is due to expire this year, and repeated his earlier proposal to spend another $342 million to add 40,000 more jobs to the Job Corps program, doubling its size.

"I hope the Congress will act quickly on this proposal," Carter said. "I might say many members of the Congress have . . . done a great deal of work on this subject even before I became President."

Carter also said at his press conference that the White House has not yet decided "how to encourage or perhaps even to force the end of wasting natural gas just for the generation of heat at central power plant stations."

"It may be done by legislation. It may be done by economic penalties. It may be done by an appeal to the stationary producers to shift on a patriotic basis. I can't yet say which of the proposals will be mandatory and which will be voluntary," the President said.