GDANSK, Poland -- With his back to a stark monument to workers slain in anti-government strikes, and his eyes gazing across a sea of hopeful faces and fluttering American and Polish flags, President Bush on Tuesday delivered an emotional plea for freedom and democracy on the site where the Solidarity trade union was born.

"Your time has come," Bush said to thousands upon thousands of Poles overflowing the grassy square just outside the iron gates of the Lenin Shipyard and spilling for blocks down the broad sidewalks of Waly Piastowskie Street.

"It is Poland's time of possibilities," Bush declared. "Its time of responsibilities. Its time of destiny. A time when dreams can live again. Solidarity reborn."

The crowd--estimated at 20,000 by some, and at 40,000 by an overenthusiastic Solidarity official--began forming at 8 a.m., six hours before Bush arrived. When he appeared at the podium, the crowd chanted in Polish, "Long live Bush!"

The speech was the capstone on Bush's two-day visit to Poland.

'Fantastic, Fantastic'

From the public reaction--at which Solidarity leader Lech Walesa marveled aloud, "Fantastic, fantastic," as he and Bush rode through streets past thousands of admirers--to the fact that the campaign-like rally could even be held at the once off-limits Solidarity monument, the tour to Warsaw and Gdansk reflected the sudden changes taking place in Poland.

During the visit, Bush prodded the nation's leaders--Communist Party officials now sharing authority with Solidarity in the Soviet Bloc's first freely elected legislature--to accept economic reforms hand in hand with political reforms as a key step in obtaining crucial Western aid to bail out a struggling economy.

Walesa, reflecting the upbeat tenor of the President's visit, responded, "We have a chance to be the America of the East."

Introducing Bush to the crowd, he said, "We are shaking off the burden of Stalinism and trying to catch up with Europe and the developed world."

But he warned that economic and political reform must work in tandem. "This is the lesson of the events in China--not balancing both spheres led directly to the massacre in Tian An Men Square."

The joint themes--of freedom and democracy, of a Europe no longer divided by the ideological and geographical boundaries of the Cold War and of political and economic reform--are the backdrop, too, for the President's visit to Hungary, his second stop on a four-nation European tour. He arrived in Budapest from Gdansk on Tuesday evening.

In sunny Gdansk--where 50 years ago this Sept. 1 some of the first shots of World War II were fired--a cool Baltic Sea breeze wafted the dark gray shipyard smoke away from the crowd, and idle cranes offered a silent, skeleton-like backdrop in the distance.

"Today, to those who think that hopes can be forever suppressed--I say, 'Let them look at Poland.' To those who think that freedom can be forever denied--I say, 'Let them look at Poland,' " Bush declared.

It was an echo of one of President John F. Kennedy's most famous speeches, delivered in the divided city of Berlin on June 26, 1963, in which he challenged those who believed that communism was the wave of the future: "Let them come to Berlin."

At the front of the crowd, Czeslaw Tolwinski, the general manager of the shipyard, sat among the dignitaries. He appeared uncomfortable amid the U.S. and Solidarity flags that shared space with the Polish flag, but he applauded politely for Bush. Tadeusz Fiszbach, the local Communist Party chief and a leading party liberal, received polite applause from the crowd when he arrived.

Asking for Seats

But two Communist Party members who serve on the Gdansk City Council had to ask the head of the Solidarity chapter at the shipyard for seats.

"Make them kneel on the cobblestones," said a man in the crowd. But eventually they were given seats on folding chairs.