Walter F. Mondale today said it was "pathetic" that President Reagan's first scheduled encounter with a top-level leader of the Soviet Union had not been arranged until Reagan was in the midst of a reelection campaign.

The Democratic presidential nominee stopped short of accusing the president of agreeing to meet with Soviet Foreign Minister Andrei A. Gromyko solely for partisan gain. "I hope he's sincere," Mondale said. "I don't want to get into a psychoanalysis of Reagan's motives ."

But he said, "It's pretty pathetic that an administration in the middle of its campaign for reelection has its first meeting not with the Soviet counterpart of the president's but with the foreign minister."

A Mondale administration, he added at an airport press conference here, would begin negotiating on arms control with the Soviets "from the first day I am president and not from the first day I seek my reelection."

Mondale said he had "urged" that such a meeting take place, was "glad" it had been scheduled and "hoped" that it would prove productive. But on the issue he and his strategists consider the president to be most vulnerable, the challenger barely paused between attacks.

"We're all well aware that on the issue of arms control, Reagan has been, and is a radical. He's opposed the efforts of every president from Eisenhower forward to control nuclear armaments, he's the first president since the bomb went off to make no progress, he's the first since Hoover not to meet with his Soviet counterpart. I hope he's learned. I hope he's changed. Because it's far too important."

Mondale had journeyed here with the intention of hammering Reagan on a different topic, the impact of his administration's high budget deficits on trade-sensitive basic American industries.

At a trade show of the International Machine Tool Manufacturers Association, Mondale said that the United States was "in open, international rout" because Reagan's deficits had driven up interest rates and overvalued the American dollar against foreign currency by 30 percent.

He said the distorted currency amounted to placing an "invisible tax of 30 percent on all U.S. exports" and then "using the proceeds of that tax to subsidize foreign competition by 30 percent." The United States, he said, had lost 3.3 million jobs in the last four years as a result.

The nominee contrasted his own willingness to disclose a $177 billion deficit reduction plan with what he called Reagan's "no problem, no plan" approach.

"Joe Louis said something I'd like to tell the president if I might. He said, 'You can run but you can't hide,' " Mondale said.

He also told the machine manufacturers that they deserve protection from foreign competition when it is subsidized by foreign governments. "You're competing not with a foreign company, but with the treasury of a foreign country, and that's one too many," he said.

Mondale was greeted here by Cook County Democratic Chairman Edward Vrdolyak, but not by Vrdolyak's arch political enemy, Mayor Harold Washington, who had told Mondale he had a schedule conflict.

Washington sent his fiance, Mary Ella Smith, among others. The Mondale camp said privately they hoped that in the city that has been described as "the Beirut of American politics," feuding between Vrdolyak and Washington over local contests will produce a large turnout and help Mondale in November.

"It's not a our job to solve the political situation in Chicago," said a Mondale aide. "We're happy to take support from these leaders individually and separately."

Vrdolyak said he believed that "if the election were held today, Mondale would carry Illinois, despite what the polls say."

A Gallup poll taken here before last month's Republican National Convention gave Reagan a three-point lead, but television polls since then show the gap is widening.