Vice President Mondale, arriving here tonight for the start of a worldwide tour of America's allies, said, "The quicker we get started" on international economic and political problems, the better the new administration's chances of success will be.

Landing in Belgium less than 80 hours after taking the oath of office with President Carter. Mondale said, "Some of the problems are pressing in on this adminsitration . . . Some of them are waiting there, ticking and they require very early attention."

The Vice President cited the urgency of action on arms control, trade and economic problems as one reason for what he called "an unprecedented . . . diplomatic mission so early in a new administration."

The other purpose, he told reporters on route here from Washington, was to find a "dramatic way" to show "the high priority we place on high-level cooperative consulations with our . . . traditional allies and friends."

Carter gave Mondale, his wife and about 45 of their former Cleveland Park neighbors breakfast at the White House this morning before seeing Mondale off on what Carter called "this very important diplomatic trip." The whirlwind, 10-day journey will take Mondale to Bonn. Berlin, Rome, London, Paris and Tokyo before his scheduled Feb. 1 return.

At the arrival ceremonies in Brussels, where he will confer Monday with leaders of the North Atlantic Treaty Organization, the European Economic Community, and the Belgian and Dutch governments. Mondale said, "My journey to Europe and Japan in the first week of President Carter's administration underlines the importance the President attaches to early consultations aimed at progress on the interests our peoples share."

The former Minnesota senator, who acknowledged that he has limited experience in high level diplomacy, told reporters "I feel ready" to represent the administration after two weeks of intensive briefings and a two-hour National Security Council meeting Saturday, where "we reviewed the substantive issues that might arise."

Within an hour after his 9 a.m. departure from Andrews Air Force Base in Air Force 2 - the same plane former Secretary of State Henry A. Kissinger used for his "shuttle diplomacy" - Mondale invited reporters into his cabin for a preview of the trip.

Unlike Kissinger, who preferred to speak as "a senior official aboard the Secretary's plane," Mondale put his remarks on the record.

The Vice President said. "There are many problems and concerns - that will be better handled the quicker we get started . . . some of the problems . . . don't necessarily follow our constitutional calendar when you assume office."

For example, Mondale said, the Strategic Arms Limitation Talks (SALT) with the Soviet Union "have just been sitting there" since former President Ford met Soviet leader Brezhnev in Vladivostok in 1974.

"Early movement on that is required," he said.

Similarly, he said, multilateral trade negotiations "have been sitting there at dead center for over a year . . . and if they don't go forward, you can expect much more protectionist forces to go into play."

"Economics is up front as on issue" in his talks, Mondale said, "because all of our nations are suffering from inflation and unemployment . . . if we could move quickly now to restore our economies to better health, there-by improving trade opportunities and employment, we can redirect our energies and not slide backward.

Dawn in the Windward Passage, the sea scarcely ripening talks that Carter himself will continue at a summit meeting of industralized countries expected to be held "later on this spring."

The President and Mondale both said there was a broader agenda for this journey, including what Carter called "the importance that we attach to the limitation on proliferation of the capability for atomic weapons."

Mondale said Carter's "deep concern" about the problem was one of the "new directions" in foreign policy he would be discussing with the allied leaders.

"This is a working trip," he said. We've indicated . . . we're not interested in ceremonial types of events . . . and we're not trying to leave a trail of headlines.

Nonetheless, Mondale is traveling with a staff of about two dozen people, and about 30 reporters and technicians form American and foreign news organizations crossed the Atlantic with him.