THE UNITED STATES has made great progress over the past two decades in opening opportunities for people with disabilities. Many other countries lag far behind. That’s why the U.S. Senate ought to ratify a U.N. treaty on rights for people with disabilities, a vote that’s scheduled for Tuesday.

Anyone who has traveled the world knows that many people with disabilities continue to face overwhelming barriers to participating in their societies. The wheelchair ramps we’ve come to expect in this country are nonexistent in many places. In developing countries, 90 percent of children with disabilities do not attend school. Huge pools of talent go to waste as a result, and millions of lives fail to reach their potential. Americans pay a price, too. Those who want to travel or work abroad encounter obstacles, and U.S. companies that pay for wheelchair ramps and other accommodations here say that they’re at a competitive advantage with overseas companies that don’t bear the same expense. (We’d argue that the U.S. firms more than make up the difference by accessing the talent of those with disabilities, but we don’t need to debate that question today.)

The Convention on the Rights of Persons With Disabilities, which the George W. Bush administration negotiated and signed in 2006, is modeled in large part on the Americans With Disabilities Act, which President George H.W. Bush signed in 1990. It would not require the United States to change its laws, but ratification would give Americans the standing to lobby other nations to follow the U.S. lead and to offer help to those who want to do so. It’s been signed by 154 countries and ratified by 124. More than 60 senators have indicated support, but backers say they are about four votes short of the two-thirds majority they need.

Opposition comes from the far right, led by former presidential candidate Rick Santorum, who says he worries that the treaty could force changes in U.S. laws. It wouldn’t. A more sober analysis from the conservative Heritage Foundation bases its opposition on the argument that the treaty would not help Americans with disabilities at home but would establish an international committee to review periodic reports from the United States and make “such suggestions and general recommendations on the report as it may consider appropriate.” Suggestions from foreign experts! The horror!

Former Senate majority leader Robert J. Dole, a Kansas Republican, helped push America’s disability act into law and is now, at 89, calling GOP senators to urge them to back ratification. “We’re the world’s leader in disability progress, and this would give us a seat at the table,” Mr. Dole told us during a phone call Sunday. “We’d be able to help other countries, because some of the smaller countries are going to need some help.”

Today’s Republican senators could do a lot worse than to heed Mr. Dole’s advice. His political career is eloquent testament that heartland conservatism is consistent with enlightened global engagement and a compassionate commitment to civil rights for all — including citizens with disabilities.