KENNEBUNKPORT, MAINE, MAY 27 -- President Bush, describing Soviet President Mikhail Gorbachev as a "tough guy" in negotiations, said that when the two leaders meet this week he hopes to narrow their differences over the role of a united Germany in Europe.

Bush, who is vacationing here before the Thursday opening of the summit, said in an interview with Soviet television broadcast there today that, in addition to the German issue, he hopes for progress on the strategic arms treaty and "more progress" on reducing conventional forces in Europe, a subject that has bogged down in recent weeks.

The president also said he would not "sweep under the rug" the issue of Lithuania and the other Baltic republics that are trying to break away from Moscow. "I have to have him understand the constraints on any U.S. president until self-determination is visible and forthcoming there," he said.

Bush said he wants to "sit and talk" with Gorbachev about U.S. "aspirations for a post-German-unification Europe. I want to convince Mr. Gorbachev . . . that the U.S. presence in Europe, a unified Germany, a Germany in NATO not only is no threat to the Soviet Union, but preserves the kind of stable Europe that the Soviets should welcome."

Acknowledging the Soviet position, reiterated by Gorbachev this weekend, that a unified Germany should not be part of the North Atlantic Treaty Organization, Bush did not suggest the two would agree. "But I want to narrow the differences. That's what I expect on that," he said.

Bush brushed aside suggestions that Gorbachev comes to the table weakened by the deteriorating economic and political situation in the Soviet Union. "It's not a question of who is stronger, who is weaker, who has got bigger problems, who has got less problems," Bush said. It is a question of trying "to convince him where we differ that our position is correct, just as he will be trying to convince me."

Secretary of State James A. Baker III, appearing on the CBS News program "Face the Nation," said the United States is "risking nothing" by negotiating with Gorbachev, despite his difficult domestic problems. If Gorbachev remains in power, "he will deliver" on any arms or other agreements that are reached now "without regard to what his future prospects are," said Baker. If Gorbachev should be overthrown, he said, "at least you have an agreement there that will make it harder for the successor government to reverse those things."

Baker said that while Gorbachev has "very difficult problems" at home, he has strengthened his political position by becoming the Soviet Union's first executive president. "In terms of a threat to him from the top, I think it's perhaps less than it was before. . . . A threat from the bottom up is greater than it was before," said Baker.

National security adviser Brent Scowcroft, appearing on ABC News's "This Week with David Brinkley," described the Soviet Union as "a society in revolution." Scowcroft, who was reported skeptical of Gorbachev's changes in the early months of the Bush administration, took a different view yesterday. "When you look at the Soviet Union in 1985 {when Gorbachev took office} and the Soviet Union now, can you not say that there are dramatic, indeed breathtaking changes?" Scowcroft asked.

Bush, in the Soviet television interview, shied from assessing his relationship with Gorbachev, other than to say it was generally good and to add he "may be mad with me over some things because we do have some differences."

He took issue with suggestions that the United States bases too much of its policies on Gorbachev personally, considering the precarious state of the Soviet Union and the risks of the reforms he is proposing. "Some of my critics . . . say, 'Hey, you're putting too much emphasis on Mr. Gorbachev,' " Bush said. "And I'm saying I know him. I'm confident we can have good open discussions. He deserves credit for what he has done."

Bush issued, as he has repeatedly during the past year, a strong endorsement of Gorbachev's economic reforms, arguing that a more prosperous Soviet Union will make for a more peaceful world and may directly benefit the United States in increased trade. "When I think of perestroika, I think of dramatic reform and change, which we salute and we want to see it continue," Bush said.

Bush, putting the talks in personal terms, noted both leaders have grandchildren and can discuss their differences "as human beings. Hey, what are we going to do to make things a little safer? If we argue, we'll do that pleasantly. He's a tough guy. He'll listen. I've been around him enough to know that he drives his point home. Well, I can do the same thing. I think it's important that I level with him."

Unlike President Ronald Reagan's pre-summit regimens, Bush appears to have engaged in little special preparation for the summit during his long weekend in Maine. Reagan routinely had days of special briefings and discussions with his top aides, but Bush has incorporated that in his regular schedule, aides said.

None of the president's top national security and foreign policy experts accompanied him here, with deputy national security adviser Robert M. Gates the only national security aide along for the four-day respite. The president has stuck to his Kennebunkport routine of running, boating, golfing and other sports. He returns to Washington Monday night.

Staff writer Don Oberdorfer in Washington contributed to this report.