WASHINGTON (AP) _ A quarter century after Congress sought to beautify the nation's highways, billboards still blight the landscape, a coalition of public officials and environmentalists say.

Giant billboards on metal posts as much as 150 feet tall have replaced the 15-foot plywood signs that dotted highways in the mid-1960s. And according to a group proposing a ban on new billboards along federal highways, advertisers have used loopholes and amendments in the 1965 highway beautification law to cut down public trees and spend taxpayer dollars to take down old signs.

''The Highway Beautification Act of 1965, despite its good intentions, has not lived up to its expectations,'' Sen. John Chafee, R-R.I., author of the billboard proposal, told the Senate Tuesday.

The answer proposed by Chafee, several Senate and House colleagues, Houston Mayor Kathy Whitmire and several environmental groups is to take power away from the federal government.

The legislation, in addition to banning new billboards on major federal highways, would allow states, cities and towns to remove existing billboards along those roadways. Using a court-tested amortization process, the communities could remove the signs in as little as five years at no cost to taxpayers, according to Chafee.

--- Cuba Extends Jamming of Radio Marti Past Sunrise

WASHINGTON (AP) - Cuba is now jamming the U.S. government's Radio Marti broadcasts in the morning hours, says a spokeswoman for the Voice of America, which runs the station.

VOA spokeswoman Beth Knisley said Tuesday that the agency deplores the action taken against Radio Marti, which began broadcasting five years ago. The jamming denies the Cuban people ''access to uncensored news and information,'' she said.

She quoted a Cuban government statement as saying that the jamming was a ''new step toward a definitive solution of the problem.'' She said the broadcast operation can still be heard on shortwave radios.

Cuba started jamming the station during the pre-dawn hours last week and then shifted the interference on Tuesday to the post-sunrise period when the audience is much greater.

The actions appear to be related to the advent of TV Marti, the televised version of Radio Marti. TV Marti tests began last month during the early morning hours and have been jammed consistently by Cuban transmitters.

--- Agency Rejects Proposal to Tax Children's Social Security Benefits

WASHINGTON (AP) - The Social Security Administration will not collect income taxes on many Social Security benefits paid to children claimed as dependents by their parents.

The agency rejected the proposal, made by the inspector general of the Health and Human Services Department, as ''anti-family'' and contrary to President Bush's goal of a ''kindler, gentler America.''

Inspector General Richard Kusserow recommended, in an audit released Tuesday, that the taxes be paid by most of the 334,000 middle- and upper- income families whose children how receive tax-free benefits.

Even as the children were receiving the tax-free benefits, about 4.5 million retirees and disabled beneficiaries and their spouses at the same income levels were paying income taxes on as much as one-half of their Social Security benefits.

In a memo included in the report, Social Security Commissioner Gwendolyn King rejected the proposal, saying she was concerned about how it would be perceived by Congress and the public.