An attorney for four Puerto Rican nationalists imprisoned for attacks on President Harry Truman and the House of Representatives announced at a rally yesterday that they will drop their federal suit for release and take their case to the U.N. Human Rights Commission.

Rally organizers said Andres Figueroa Cordero, who also was convicted in the March 1, 1954, attack on the House, made a brief appearance before the demonstrators as they assembled on the Washington Monument grounds.

Figueroa was ordered released last year by President Carter because Figueroa is dying of cancer. Due to his condition and the 97-degree heat, organizers said Fegueroa did not attend the rally and was whisked away to catch a plane for Cuba, where he is to take part in a July 26 celebration there.

Some 300 to 400 demonstrators marched around the White House to the southwest corner of Lafayette Square, where they held a two-hour rally one-half block from Blair House, where the Nov. 1, 1950, Truman assassination attempt in the death of a Puerto Rican. Griselio Torresola, and a Secret Service guard and the imprisonment of nationalist Oscar Collazo.

Michael Deutsch of Chicago, an attorney for the national committee to free the four Puerto Rican prisoners, which sponsored the rally, said he would tell the U.S. District Court tomorrow that suit, filed in November 1976, to free the four nationalists and Figueroa.

The four are Collazo, Lolita Lebron Irving Flores and Rafael Cancel Miranda.