MOSCOW, JAN. 1 -- It was only on one of the three television channels and it was upstaged by an address by Soviet leader Mikhail Gorbachev, but still a five-minute New Year's greeting by President Reagan to the Soviet people tonight seemed certain to attract a big audience here.

The prominence of the leaders' twin messages and their joint pledges for further "interaction" put U.S.-Soviet relations at the center of Soviet public attention and at the top of the Soviet agenda for 1988.

Aired at 7 p.m. Moscow time, Gorbachev's and Reagan's addresses, sandwiched between an adventure film and a traditional New Year's variety show, had been well advertised in today's television listings.

In 1986, Reagan's address was the lead item on the Soviet evening news program "Vremya."

The president was a novelty to Soviet viewers at the time: his New Year's greeting marked the first time since 1972 that an American leader had addressed the Soviet people.

He and Gorbachev had met for the first time in Geneva two months earlier. It was the beginning of their relationship.

Last year, there were no greetings amid a chill in U.S.-Soviet relations after the summit three months before in Reykjavik, Iceland, where Gorbachev and Reagan had parted after a disappointing encounter.

In 1987, there was the summit in Washington and the signing of a treaty to eliminate intermediate-range nuclear weapons.

Tonight's messages seemed to ride the latest and most optimistic wave of U.S.-Soviet relations during the Reagan presidency.

By touching on themes of American religious observances and of the coming U.S. elections, Reagan hinted at the differences between the political systems in the two countries.

His oblique reference to the Afghanistan conflict and his defense of the Strategic Defense Initiative, his controversial space defense program, hit on issues that still divide Moscow and Washington.

"Silence is a form of falsehood," he said about American concern for human rights.

But overall, to a Soviet audience, the tone of Reagan's address was mild and upbeat, confident and not aggressive.

It went further to complete the change in Reagan's image that evolving policies and the Soviet media have combined to reconstruct over the past two years.

Once seen here as a trigger-happy cowboy, Reagan is now presented as a more avuncular figure, an elderly leader in his waning days of power.

During the Washington summit, people here watched with pleasure as he gave a smooth, self-assured performance, gamely attempting to translate Russian proverbs.

Not all Soviets are convinced that Reagan's anti-Soviet feelings have diminished, and many worry that the good will that now seems to dominate the public side of superpower relations is somehow a trick.

But Reagan's repeated appearances on television and in the press -- two interviews with the president have been printed in a leading Soviet newspaper in two years -- have at least served to demystify him as a character, if not to dispel doubts about his intentions.