MOSCOW (AP) _ Soviet television programming was interrupted Sunday by a live broadcast of Kremlin leader Mikhail Gorbachev's announcement in Iceland that he and President Reagan had failed to reach arms control agreements.

The television carried Gorbachev's 45-minute news conference in Reykjavik in full, with questions to the Kremlin leader in English being translated into Russian for watching Soviet citizens.

There was no report on separate comments by Secretary of State George Shultz about the two-day summit.

The official news agency Tass swiftly put out excerpts of Gorbachev's statements, but made no commentary.

Gorbachev said he made major concessions at the summit, but that the meeting fell apart in a dispute over Reagan's ''Star Wars'' space-based missile defense research.

Before the news conference began, the television showed Gorbachev's wife Raisa coming into the hall where it was held. The camera turned to her several times while her husband spoke.

An hour before the Gorbachev-Reagan talks ended, Valentin Zorin, senior commentator on U.S. affairs, spoke in a hopeful mood during a brief report from Reykjavik for the national evening television news.

Two hours before that, however, on a current affairs program, Zorin accused ''some people, in particular the opponents of Soviet-American dialogue'' of ''trying to muddy the waters in every possible way.''

Newspapers on Sunday devoted much attention to the Iceland meetings, and criticized a White House proposal to revive threshhold treaties on nuclear testing instead of agreeing to an outright test ban.

''Sour milk will not become fresh, even in a new bottle,'' the Communist Party daily Pravda said.

Pravda and other national newspapers also carried front-page pictures showing Gorbachev and Reagan together before the talks began Saturday.

It was a rare photo appearance for Reagan in the Soviet press. The last time newspapers published front-page pictures of the president was during the superpower summit in Geneva last November.

Coverage of the meetings was relatively restrained and concentrated on restating known Kremlin positions and reporting events surrounding the talks.

Pravda criticized Reagan's plan to ask Congress for ratification of the 1974 Threshhold Test Ban Treaty.

It also suggested that White House spokesman Larry Speakes violated a confidentiality agreement by telling reporters about it on Friday.

Speakes told a briefing in Reykjavik that Reagan would tell Gorbachev he planned to ask for ratification if the Kremlin leader agreed to bolster the treaty's verification provisions.

''The problem of 'threshholds,' which establish limits on the number of kilotons, is a problem of yesterday,'' the newspaper said. ''And now one should speak not about threshholds ... but about their (nuclear tests') full prohibition.''

The Soviet Union's 14-month-old unilateral nuclear test moratorium and its calls for the United States to also halt testing have become a cornerstone of Kremlin arms control policy.