Sen. Charles Percy arrived here today hoping to tell Soviet President Leonid Brezhnev that the new Reagan administration is ready to "sit down as long as it takes" to negotiate limits on strategic weapons.

Percy (R-Ill.), slated to be Foreign Relations Committee chairman when the Republicans take control of the Senate in January, called his visit "a first official step, closely coordinated" with President-elect Ronald Reagan, to lay out its views. He has asked to see Brezhnev and other senior Soviet officials for talks next week.

"The main object is to begin the discussion," Percey said at a brief airport press conference. The Soviets must "take into account . . . there is linkage" in the Reagan view of bilateral relations, he asserted, specifically naming the Afghanistan invasion and fears of Soviet intervention in Poland as matters that affect Soviet-American relations in general.

There is "not a confrontational atmosphere" within the new Republican high command, Percy said. "Our goal is clarity." He said the Soviets appear equally interested in opening a dialogue with the new administration, agreeing that Brezhnev's speech Tuesday promising "a positive reaction" to "any constructive steps" by Washington was a strong indication of the Kremlin mood.

"The Reagan administration sends signals and it is important that this leadership sends signals," he said.

Percy said the SALT II treaty, stalled by President Carter in the Senate after the invasion of Afghanistan last December, would "never have been ratified" without changes anyway, regardless of what Moscow may have wanted.Reagan has said he wants to scrap the treaty and negotiate a new one. Percy said this concept is aimed at achieving actual decreases in warheads for both sides.

Percy said he had talked not only with Reagan but with the president-elect's aides and Carter administration people as well before coming here.