The House plans to trigger a new veto showdown with President Bush next week by clearing legislation to expand federally funded embryonic stem cell research.

Bush has vowed to veto the measure (S 5), just as he vetoed similar legislation last summer. A veto override attempt in the House last year fell 51 votes short of the two-thirds majority required.

This year, the Senate passed the stem cell bill by 63-34 on April 11. After accounting for absentees, supporters of the measure believe they are just one vote short of the two-thirds majority needed to override a veto in the Senate.

But even if the bill’s supporters could win a Senate override vote, they stand little chance of success in the House, which passed its own stem cell bill on Jan. 11 by 253-174. That was 32 votes short of a two-thirds majority.

Nonetheless, Democrats see the stem cell issue as a political winner. Polls show broad public support for such research for its potential to produce treatments for a wide range of disabling conditions.

Under an order Bush issued Aug. 9, 2001, federal money is available only for research on embryonic stem cell lines derived before that date. Scientists say there are far too few such lines, and many are contaminated.