OTTAWA, MAY 29 -- A smiling and outwardly confident Soviet President Mikhail Gorbachev, showing no sign of tension over his mounting political problems at home, arrived here today for meetings with Canadian officials prior to his summit in Washington with President Bush.

Within moments of a welcoming 21-gun salute and other traditional airport ceremonies, Gorbachev plunged into a crowd of Canadian schoolchildren, shaking hands and signing autographs, more in the manner of a front-running political campaigner than the beleaguered head of a country in the midst of economic crisis and ethnic turmoil.

Noting the "dramatic changes in the world," Gorbachev called in brief airport remarks for a renewal of dialogue and trust among world leaders as a "modern Europe" is crafted through negotiations and statesmanship.

Later, the Soviet leader quipped lightheartedly about Canada's clean air, saying that "there has to be a special tax on their oxygen." His host, Prime Minister Brian Mulroney, who has been beset by his own political problems and a diminishing public-approval rating, interjected: "I want all Canadians to know that the idea for a new tax in Canada came from President Gorbachev and not me. I've got enough troubles right now."

Soviet Foreign Minister Eduard Shevardnadze told reporters later that Gorbachev's war of nerves with the independence-minded Soviet Baltic republics and the election of Gorbachev's outspoken political rival Boris Yeltsin as president of the powerful Russian republic had done nothing to diminish the Soviet leader's domestic position as he moves on to Washington Wednesday.

In response to questions at a news conference, Shevardnadze said: "I can't sense any weakening of the president's position, and I work with him closely day to day in Moscow. As to the election of Yeltsin . . . this is something that I don't think should be viewed as an out of the ordinary event. Against the backdrop of glasnost {openness} and developments in the Soviet Union, this decision by the voters is something we should not feel very surprised about."

After two lengthy meeting with Canadian External Affairs Minister Joe Clark, Shevardnadze said that while differences remain between Moscow and Washington over the political and military future of a unified Germany, he believes the gap has been narrowed on the role to be played by the 35-member Conference on Security and Cooperation in Europe. Canada has argued that the CSCE's function should be broadened to include talks on conventional-arms reductions in Europe.

"It is difficult to say; the summit is only the day after tomorrow, but I don't think there's going to be much difference" in the superpower positions, Shevardnadze said.

Clark said that Canada's position on the future role of the CSCE, which is close to that of the United States, "has a lot in common" with the views he heard today in his talks with Shevardnadze. Clark said he also brought up the subject of Lithuania's declaration of independence from the Soviet Union and had received encouragement that the matter could be resolved by negotiation.

Gorbachev's visit, which the Canadian press has called the "bed and breakfast summit" because of its 36-hour duration, was relatively low-key today as the Soviet leader and his wife, Raisa, visited Mulroney's official residence, took a brief walk around central Ottawa and then rested for a round of official functions here Wednesday before flying on to Washington.

Gorbachev turned down an invitation to address Parliament, telling Canadian officials he would rather use his short time here for more personal discussions. He also asked for a light schedule and light meals to allow himself time to adjust physically after the long flight from Moscow.

As it happened, Clark had to leave his meeting with Shevardnadze at one point to vote in Parliament on a controversial abortion bill that will require any woman seeking an abortion to obtain a physician's certification that termination of a pregnancy is necessary to maintain her physical or psychological health.

Asked if he had discussed with Clark the political tensions in Canada over a revived separatist movement in the predominantly French-speaking province of Quebec, Shevardnadze said that they had talked about internal developments in the Soviet Union but had not had time to discuss the Quebec issue. He said he hoped to cover that topic in conversations Wednesday.

Shevardnadze laughed -- apparently over the similar political problems posed by cultural and linguistic minorities in both countries -- when Clark told an inquiring reporter at the news conference: "Nice try, anyway."

Clark and Shevardnadze said they also had discussed bilateral issues, focusing in particular on environmental problems in the Arctic, where the Soviet Union plans to resume underground testing of nuclear weapons after 1993. Canada has opposed a resumption of nuclear testing in the Arctic because of the danger of venting radioactive materials into the atmosphere and the possible effects on the environment.

The Soviet delegation received a hearty welcome on its arrival at Uplands Air Force Base, outside the capital, as several hundred Canadians applauded the Gorbachevs and the Royal Canadian Regimental Band played both the "Internationale" and "O Canada."

Gorbachev said he had "warm memories" of Canada, referring to a 1983 visit here as a relatively unknown agriculture minister in which he nurtured the seeds of glasnost and perestroika (restructuring) in long conversations with then-Soviet ambassador to Canada, Alexander Yakovlev. Yakovlev, a chief architect of the Soviet reform drive, is now Gorbachev's closest ally in the Kremlin leadership.