Soviet President Mikhail S. Gorbachev and Prime Minister Margaret Thatcher argued passionately Thursday during a four-hour meeting that covered subjects ranging from disarmament to reports of Soviet bomber sales to Libya, officials said.

Reopening a European peace offensive that was disrupted by the Armenian earthquake, Gorbachev had "extremely frank exchanges, animated, warm, passionate and solemn," said a Thatcher spokesman, requesting anonymity.Gorbachev also hit the streets of London, stopping his motorcade to shake hands outside Westminster Abbey.

The Thatcher spokesman said the Soviet leader and the anti-communist prime minister "love arguing."

The spokesman said Thatcher asked Gorbachev about a report from Washington that Moscow sold up to 15 long-range fighter-bombers to Libya, which Britain accuses of sponsoring terrorism. Gorbachev did not respond, he said.

He said Thatcher also accused the Soviets of having been "not as frank as they should be" about their chemical weapons.

He quoted Gorbachev as replying: "If you aren't fully satisfied, then quite clearly we have to have more exchanges. We have got to try better to convince each other."

Another area of disagreement was Gorbachev's goal of eliminating all nuclear weapons from Europe.

Arriving at Thatcher's residence, he waved and smiled to onlookers and was applauded by office staff who lined the corridors.

Gorbachev's wife, Raisa, went sightseeing in London, starting at St. Paul's Cathedral where she gave a bear hug to a 4-year-old girl who presented her with a bouquet.

Tim Haggarty, 23, from Northern Ireland, who waited in the rain for 90 minutes to be first to shake hands with Gorbachev, said afterward: "He's trying to create peace in the world. He has to be treated like the hero he is."

The two leaders also signed an agreement for British contractors to build a $7 million school in Leninakan, a city devastated by the Armenian earthquake.

Gorbachev arrived late Wednesday night from Cuba, where he proposed making Latin America a "zone of peace."

But his rhetoric about Latin America has failed to convince the Bush adminstration.

In Washington, White House Press Secretary Marlin Fitzwater said Bush is disappointed that Gorbachev is not withdrawing military support from Nicaragua.

"While his words about not exporting revolution are welcomed, they are not matched by deeds which would give those words credence," Fitzwater said Wednesday.

The White House called on Gorbachev to back up his statements about wanting demilitarized peace zones in Central America, by discontinuing military assistance to the leftist government of Nicaragua.