Live from the roof of the Caravelle Hotel, old Saigon hand Steve Bell of ABC Television was doing the first satellite broadcast to American viewers from this former South Vietnamese capital when an enormous rat trundled out to investigate.

Apparently "mystified" by the lights and cameras and taking a proprietary interest in the proceedings, as one ABC correspondent described it, the rodent reared up on its hind legs and sniffed at Bell's pant leg. Producers and cameramen of "Good Morning America" were briefly paralyzed by indecision: whether to warn Bell, who had not noticed the rat, and risk spoiling the first live broadcast from Ho Chi Minh City, or do nothing and risk letting the rat bite one of their star reporters.

In the end, they did nothing, and the rat ambled peaceably away.

The show must go on, and so it does as America's networks and the rest of a foreign press corps of nearly 200 scramble to cover Vietnam's celebrations marking the l0th anniversary of the fall of Saigon. NBC, with Bryant Gumbel cohosting the "Today" show here by satellite from a mobile ground station, is claiming the first live broadcast of a regular U.S. television show from Ho Chi Minh City, formerly Saigon. But ABC, with its transmission Tuesday night via a Soviet ground station and satellite, claims the first live broacdcast of any description.

Also here for ABC is Ted Koppel, who hopes to make news with a live, two-way interview with former Paris peace negotiators Le Duc Tho and Henry Kissinger Tuesday morning (Monday night U.S. time). Le Duc Tho, a senior member of the Hanoi Politburo, is to be interviewed by Koppel here -- if all goes well -- after a parade marking the Communist "liberation" of Saigon on April 30, 1975. Vietnamese authorities say more than 100,000 civilians, plus military units, will march.

Le Duc Tho refused to share the Nobel Peace Prize with Kissinger after the two men negotiated the short-lived Paris agreement, and they have since made acrimonious public references to each other.

Gumbel recorded a two-hour videotaped interview with Le Duc Tho today for broadcast Monday.

CBS has kept out of the expensive live-TV competition but has been running taped spots on its news programs and is here to cover the 10th anniversary.

The battle of the networks and the media scramble in general have left correspondents here with a chicken-or-egg puzzle. Did the Vietnamese plan to make the 10th anniversary an occasion for such major nationwide celebrations, parades and ceremonies in the first place, or has the press provided the impetus by turning the anniversary into an international media event? Indications are of a bit of both.

Asked why Hanoi has allowed about 100 American reporters, photographers and TV crew into the country to do stories related to the 10th anniversary, an official of Vietnam's Foreign Press Center told one correspondent: "Because you all asked for visas."

"If we all hadn't applied for visas," an American network cameraman quipped, "there would have been two roller skaters and a dancing girl going down the street in the April 30 parade."

However, a senior Vietnamese Foreign Ministry official said the Politburo decided last year to celebrate four anniversaries this year, including this one.

In any case, Vietnamese leaders now are calling the occasion "the greatest victory in Vietnamese history in the last 30 years" and making a major effort for what the Foreign Ministry official called "people-to-people contacts" with Americans, bypassing the U.S. government.

Apparently impressed by the lavishness of network spending on the event, Vietnamese from the Hanoi government to Saigon pedicab drivers have been seeking to cash in. As some correspondents see it, Hanoi seems to view the whole event as an opportunity to build up its foreign-exchange reserves, which now stand at about $16 million.

The government requires that correspondents pay in U.S. currency for hotels, transportation, interpreters and organizing fees. One correspondent was even presented a bill for expenses involved in flying MiG jets and driving tanks in military exercises that he was allowed to film. He refused to pay.

Another television reporter who wanted to fly from here to Hanoi was told that the flight was canceled. After chartering a Vietnamese airliner at a cost of several thousand dollars, he discovered it was the same plane as the "canceled" flight, and the Vietnamese then sold off the empty seats to other passengers.

Among correspondents' other trials are Saigon's ever-present rats. An Irish correspondent woke up to find one on his hotel bed and was bitten on the hand when he tried to knock it away. Annoyed when colleagues found humor in the incident, he warned, "If I get rabies, I'm going to bite every one of you guys."

The networks have amazed the Vietnamese by bringing in tons of equipment -- including NBC's three-ton ground station -- and chartering flights to and from Bangkok for their stars. NBC even planned to fly in 800 cases of beer for its 34 personnel during their stays of up to two months, according to one insider, until it was discovered that imported Heineken and other beers were plentiful on Saigon's black market.

NBC sources say the network is spending more than $1 million on its Vietnam coverage. ABC says it is spending around $700,000.

The Vietnamese grab for the big network bucks seem to have been spurred not only by media extravagance in what is one of the 20 poorest countries, but a suspicion that the capitalistic Americans are reaping big profits from the deal.

After installing its rented British ground station outside Saigon's former presidential palace under a $70,000 agreement with the Vietnamese administration -- down from a $400,000 asking price -- NBC started taking in large fees from other foreign television companies that wanted to use the facilities. Anxious to get in on the action and finding its sovereignty impinged, Vietnam objected and insisted on receiving payment also. Dickering continues.

Meanwhile, Gumbel is going ahead with his segments on the lawn of the floodlit palace despite being pestered by large flying insects attracted by the camera lights. The "Today" show segments are broadcast at night here because of the time difference.

Gumbel acknowledged that viewer interest is a question mark. "I think we had a responsibility to be here," he said. "When the bottom line is written, I think it will be pretty good."

Hoping to emulate his performance in Moscow last year during a similar series of programs, Gumbel said the Vietnam shows will contribute to a more serious, news-oriented image for the show.