Petitions, letters and a half-mile-long string of postcards were delivered to the White House yesterday with a plea that President Reagan and Soviet leader Mikhail Gorbachev take steps to achieve a nuclear test ban treaty at their summit meeting in Geneva next week.

The mail, collected from around the nation and abroad via a "Peace Post Office" set up in Farragut Square, included a range of presummit messages for the president.

Nobel laureate Linus Pauling, 84, called U.S. cooperation with the Soviet Union "the road to mutual prosperity and peace." And a 7-year-old school girl from California named Alison expressed a wish to hug the president and asked, "Why do we have to fight with other people from the Soviet Union?"

The White House mail delivery, sponsored by Women Strike for Peace and the Women's International League for Peace and Freedom, was just one of several summit-related demonstrations scheduled here and elsewhere by groups hoping to catch the attention of Reagan and the Soviet leadership.

On Thursday and again yesterday, for example, delegates to a national meeting of the Council of Jewish Federations joined others in a vigil across the street from the Soviet Embassy to protest the treatment of Soviet Jews.

At least two of the delegates, according to organizers, managed to gain entrance to the embassy long enough to deliver letters denouncing the harassment and imprisonment of Soviet Jews and the Soviet government's restrictive policies toward Jewish emigration. Other letters are being mailed to the embassy because officials there seldom accept such correspondence in person.

"It was supposed to be a small, quiet vigil, but once word got out, everybody wanted to do it," said Tina Begleiter, the council's consultant for special projects.

Begleiter said more than 600 demonstrators, representing about 3,500 delegates attending the council's 54th general assembly at the Washington Hilton, were bused to the embassy over a period of two days.

In addition, she said, Avital Scharansky, wife of imprisoned Soviet dissident Anatoly Scharansky, held a three-day hunger strike and delivered a letter addressed to Gorbachev to an embassy official on behalf of her husband. She was accompanied on the Wednesday visit by several members of Congress as well as members of the Rabbinical Cabinet of the United Jewish Appeal.

Begleiter noted the participation of the Jewish Community Council of Greater Washington, which holds a daily embassy vigil, and the National Conference of Soviet Jewry. She said that several representatives of Jewish groups in Canada and Mexico also joined the protest.

"I think North America Jewry made its collective statement to the U.S.S.R.," she said.

Yesterday's "Peace Mail" demonstration in Farragut Square drew about 50 participants. They held a news conference, displayed a part of the "world's longest postcard" -- actually more than 3,000 postcards tied together by purple ribbons -- and later marched to the White House.

The postcards, solicited from around the world, were assembled by the Mid-Peninsula Peace Center in Palo Alto, Calif.

"We're not opposed to cultural agreements," said Edith Villastrigo, referring to the president's call Thursday night for more cultural and scientific exchange with the Soviet Union. "But they can be signed any day of the week. I think a summit is somewhat different."

Sara Dougherty, a 9-year-old from Westchester, Pa., brought colorful paper cranes instead of letters for the president. She said the birds were made by her school classmates and symbolized life and peace.

"People die" from nuclear weapons, she said. "I don't think it's right, and I hope Reagan learns."

D.C. City Council member Hilda Mason (Statehood-At Large) said the mail being delivered to the White House carried "our hopes for global security." She said Americans would rather have a nuclear arms agreement than "a cultural honeymoon," and she asked Reagan to "use your charm but keep in mind that the people in the United States want meaningful talks leading to real security."

At the White House, the peace activists released several dozen blue balloons, each carrying the message, "Let Your Hopes for the Summit Soar." Some got caught in trees, but most, caught in an autumn wind, floated over the White House grounds and drifted between the president's home and the Executive Office Building.

On Sunday, the Jewish Community Council of Greater Washington will hold a presummit rally for Soviet Jews, beginning at 1 p.m. in Lafayette Park. Demonstrators plan to march past the White House and the Soviet Embassy.

Also Sunday, area physicians have planned their own presummit demonstration at the White House and the Soviet Embassy, and will be presenting letters for both Reagan and Gorbachev urging arms control progress.

On Tuesday, the first day of the two-day Geneva meeting, 700 members of the National Council of Jewish Women plan to hold a silent vigil outside the Soviet Embassy on behalf of Soviet Jews.