More than 1,300 scientists in 50 states have signed a letter, sent today to President Bush, asking him to endorse a bill to expand federal financing for stem-cell research.

Mr. Bush promised a veto after Congress sent him the bill last week, although he has yet to actually break out his veto pen. The scientists sent the letter hoping to persuade him to reconsider.

“Members of the House [of Representatives] had said to us that we need to hear from more scientists on this, that we think it would be helpful,” said Sarah Youngerman, a spokeswoman for the Coalition for the Advancement of Medical Research, an advocacy group that supports the bill (S 5).

The letter signers work at more than 500 research institutions, most of them universities. Those with the most signatories were Columbia University, with 47; Harvard University and the University of Massachusetts, tied at 35; and the Johns Hopkins University, 25. —Jeffrey Brainard