A bipartisan coalition of 14 senators said Tuesday that they were sending King Abdullah a letter urging him to end the Saudi ban on women driving in the conservative kingdom, the only nation in the world that prohibits women from driving or obtaining a driver’s license.

“The prohibition on women driving motor vehicles, even in cases of emergency, makes it impossible for citizens to exercise a basic human right,” the senators wrote. “We strongly urge you to reconsider this ban and take an important step toward affording Saudi women the rights they deserve.”

Following a social media campaign by rights advocates, Secretary of State Hillary Rodham Clinton said last month that she supported Saudi women who have been fighting for the right to drive but that the “effort belongs” to those behind it, signaling that the United States would not push further. The State Department has said that Clinton has also engaged in “quiet diplomacy” on the issue.

The letter released Tuesday was signed by 14 of the 17 women in the Senate. Other lawmakers, including House minority leader Nancy Pelosi, have also offered their support to the Saudi campaign.