DALLAS (AP) _ Ross Perot promised Monday to lay out the ''scope and the magnitude'' of the nation's economic woes in a 30-minute commercial he said would be the first in a series.

''It's such a massive problem, you have to take it a piece at a time,'' said Perot, who joined the presidential race last Thursday.

He said his advertising campaign, which begins with a half-hour show Tuesday and continues with a 30-minute spot on Friday, ''will be kind of like the old Superman serial ... stay tuned tomorrow and we'll go to the next phase.''

Aides declined to provide details of the commercial, Perot's first since he began talking about joining the campaign last spring.

Perot said he personally put together the 30-minute ad, and added, ''I wrote the script and drew the charts.'' He said he hopes to help the American people ''understand the size, the scope and the magnitude'' of the country's economic problems.

Before he dropped out of the race in July, Perot wrote a never-delivered campaign speech accompanied by 21 color charts showing the decline of the nation's growth, productivity and investment rates. His book, United We Stand, starts off with a chapter laying out the country's economic problems and including some of the same charts.

Perot is paying $380,000 to run his 30-minute show on CBS before the National League playoff game in the eastern half of the country and after the game in the west.

Perot spokeswoman Sharon Holman, who announced plans Sunday for a 60-second commercial on ABC's ''Monday Night Football,'' said the idea was later scuttled.

Though he did not rule out short ads, Perot said on NBC's ''Today'' show, ''You can't cover much in one minute. We need to get down in the trenches and really diagnose the problem, explain to the American people where we are, what we have to do. That's what we'll be trying to do.''

Perot's economic program calls for attacking the deficit through higher taxes, lower entitlement payments and an across-the-board government spending cut.

For the time being, the ad campaign is the chief tool of the Dallas billionaire's independent drive for the White House. Aides said Perot had no public appearances lined up this week and was preparing for Sunday's debate with President Bush and Bill Clinton.

Perot's ad was produced by The 270 Group, a consortium of Dallas ad agencies and freelancers that was hastily formed to work on the campaign. Much of it was filmed in the few days since Perot's formal entry, said a source involved in the production who asked not to be named.

The 270 Group is led by Dennis McClain, president of Temerlin McClain, a $400 million ad firm that is the largest in the Southwest. Perot said he would be interested Wednesday morning to see the overnight Nielsen ratings of TV watchers.

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