U.S.-funded programs to beat back online censorship are increasingly finding a ready audience in repressive countries, with more than 1 million people a day using online tools to get past extensive blocking programs and government surveillance.

But the popularity of those initiatives has become a liability.

Activists and nonprofit groups say that their online circumvention tools, funded by the U.S. government, are being overwhelmed by demand and that there is not enough money to expand capacity. The result: online bottlenecks that have made the tools slow and often inaccessible to users in China, Iran and elsewhere, threatening to derail the Internet freedom agenda championed by the Obama administration.

“Every time we provide them with additional funding, those bottlenecks are alleviated for a time but again fill to capacity in a short period of time,” said André Mendes, director of the Office of Technology, Services and Innovation at the Broadcasting Board of Governors (BBG), which funds some of the initiatives. “One could reasonably state that more funding would translate into more traffic and, therefore, more accessibility from behind these firewalls.”

The United States spends about $30 million a year on Internet freedom, in effect funding an asymmetric proxy war against governments that spend billions to regulate the flow of information. The programs have been backed by President Obama, who promoted the initiatives at a town-hall-style meeting in Shanghai three years ago.

During his debate last week with Republican presidential candidate Mitt Romney, Obama briefly raised the topic of government surveillance in China, accusing the former Bain Capital chief executive of investing in firms that provide surveillance technology to China’s government.

For his part, Romney has repeatedly criticized the Obama administration for what he calls its failure to stand up to the authoritarian governments in China, Iran and other countries where Internet freedom is curtailed. The two candidates meet Monday for the third and final debate, this one focusing on foreign policy.

The U.S. government funds nonprofit groups and others to develop software that can be downloaded by users in other countries with pervasive censorship. The most widely used tools route Internet traffic through other countries, allowing users to bypass Internet firewalls as well as surveillance.

The task of keeping the Internet free, however, is becoming harder.

China’s “Great Firewall” has grown more sophisticated in recent years, with the Communist government employing tens of thousands of monitors to filter content and watch users. Iran, meanwhile, has stepped up its already-substantial censorship efforts amid a mounting economic crisis, instituting new bans on overseas audio and video content and advancing plans for an Iran-only intranet.

The online crackdown is spurring calls from Internet freedom advocates for the Obama administration to step up its own efforts. Many have expressed frustration with what they perceive as slow progress advancing these tools.