Washington

With the US Senate set to debate legislation on human cloning over the next few weeks, senators are lining up behind two rival positions on the issue.

On 24 January, senators Tom Harkin (Democrat, Iowa) and Arlen Specter (Republican, Pennsylvania) introduced a bill that would allow cloning of human embryos for research purposes, but ban its use in human reproduction.

This legislation is similar to a bill introduced last month by Dianne Feinstein (Democrat, California). For jurisdictional reasons, Feinstein's bill is more likely to make it to the Senate floor, where it will compete with a proposal from Sam Brownback (Republican, Kansas) that would ban cloning for any purpose.

Most research organizations, including the Federation of American Societies for Experimental Biology and the Association of American Medical Colleges, have backed the Feinstein bill.

The Senate has yet to take a vote on the politically charged issue of cloning, although Senate majority leader Tom Daschle (Democrat, South Dakota) has responded to increasing pressure to do so by promising to allow time for a debate during February or March. The House of Representatives passed a ban on cloning for research or reproduction last July by a margin of 265 to 162.

But Congress may still fail to agree on legislation. The Senate is thought to be closely divided on the issue, but if it passes the Feinstein bill, it is highly unlikely that House and Senate negotiators would be able to agree a compromise on the basic issue of whether cloning should be permitted for research purposes.