The Senate, warned against making any changes, rejected Wednesday the first two in a series of Republican-sponsored amendments to the omnibus trade bill, indicating almost certain passage by the end of the day.

The Senate, with Democratic and Republican leaders joining to turn back all amendments, was poised to approve the bill and send it to the White House.President Reagan, who vetoed the original version of the bill, was expected to sign the legislation, considered one of the blue-ribbon bills of the 100th Congress.

The Senate defeated 69-26 an amendment by Sen. Malcolm Wallop, R-Wyo., which would continue to give the president - not the U.S. trade representative - the power to make the final determination of unfair trade practices by foreign nations.

Earlier, the Senate killed 54-32 an amendment by Sen. David Durenberger, R-Minn., which would have continued the quarter-century ban on the import of furs from the Soviet Union until the Soviets adopt a policy of free emigration.