President Reagan today told a group of Polish-Americans that the United States is prepared to lift economic sanctions against Poland if the military regime there eases its tight grip on the Polish people.

Reagan, speaking outdoors on a grassy slope behind the Polish National Alliance Hall, told the crowd, roused by Pope John Paul II's visit to their motherland this week, that it "was an inspiration to all who cherish freedom."

Reagan repeated three demands--an end to martial law, the release of political prisoners and the restoration of freely formed trade unions--that he said would be evidence of attempts at a "national reconciliation" by the government of Gen. Wojciech Jaruzelski. He said the United States and its NATO allies are ready to help Poland if those steps are taken.

"We are currently consulting with our allies on the Polish question," Reagan said. "Once these consultations are complete, we'll decide on how to proceed in our relations with Warsaw. In the meantime . . . , if the Polish government takes meaningful, liberalizing measures, we are prepared to take equally significant and concrete steps of our own."

According to administration and NATO officials, the western allies are anxious to see how the Polish government will react after the pope's visit. The officials said there will be a decision by late July on whether the Polish government's actions merit lifting the sanctions against the country.

These include denial of trade benefits, strict limits on Polish fishing rights and civil aviation, bans on further extensions of official credit and credit insurance and limits on cultural exchanges.

Earlier this month Poland asked western banking officials for an eight-year moratorium on interest payments as well as rescheduling of its $25 billion foreign debt. The government hoped to use the pope's visit as a good-will gesture to the West as it asks for help with debts that could damage the nation's economy.

"The need for dialogue and reconciliation in Poland has never been more evident than it was during the pope's visit . . . ," Reagan said. "I suspect that the Polish people are even more ready in the aftermath of his visit to begin a dialogue.

"But the real question is not the willingness of the Polish people, but that of the Warsaw government. I urge the Polish authorities to translate the restraint they showed during the papal visit into willingess to move toward reconciliation rather than confrontation with the Polish people."

Reagan added that the United States is giving Poland more than $40 million in aid and reassured those in the audience who have organized to send food and medical supplies to that nation that "if the Polish government will honor the commitments it has made to basic human rights, we in America will gladly do our share to help the shattered Polish economy, just as we helped the countries of Europe after both world wars."

He said that in "eight short days" the pope has inspired the Polish people to "continue their struggle" and that "freedom-loving people everywhere support His Holiness' call for social renewal, social justice and reaffirmation of national sovereignty."

Sen. Charles H. Percy (R-Ill.), who traveled to Chicago with the president after visiting the pope two weeks ago in Rome, said of the pope: "The guy's got guts. He's creative. He goes right in there and stops just short of stirring up rebellion."

Reagan then took a defensive stance in addressing the American Medical Association's house of delegates. He said that, although the group does not support his administration's proposal for a one-year freeze on the pricing list used by the government for medical treatment of Medicare patients, it "is painful but necessary medicine."

After acknowledging his differences with the AMA on the issue, Reagan said he'd "like to explain a proposal you don't support . . . . These payments have increased 21 percent and are expected to rise 19 percent in 1983. We believe physicians, too, must share the burden of slowing the rise in health-care costs."