ON A bluff above the river Vakhsh, Rogun’s ramshackle square boasts at least four billboards featuring Tajikistan’s president, Emomali Rakhmon, and his aphorisms, such as “Rogun is the bright future of Tajikistan”. Rogun is both a town, some 100km (60 miles) from the capital, Dushanbe, and a long-stalled dream: to build the world’s tallest hydropower dam.

Dirt-poor but water-rich, Tajikistan hopes to sell electricity to Afghanistan and South Asia. In theory, the dam, 335 metres high, could save the country from poverty and isolation, doubling Tajikistan’s power-generating capacity. But the project seems quixotic, if not outright delusional: it would cost up to $6 billion (GDP in 2012 was about $7.6 billion); Uzbekistan, a big neighbour, is fiercely opposed; and the investment climate is clouded by corruption.

Plans for the dam were drawn up long before the collapse of the Soviet Union, but were revived in the early 2000s as Tajikistan recovered from civil war. Each winter energy shortages shave an estimated 3% off GDP. Rogun will solve all problems, state propaganda and many Tajiks say.

But international donors struggle to trust Mr Rakhmon. Two-fifths of Tajikistan’s electricity is diverted to a state-run aluminium smelter, TALCO. Each year, TALCO produces hundreds of millions of dollars in profits that are routed to a shell company in the British Virgin Islands. Mr Rakhmon personally oversees TALCO. Why does he not use that cash for his dam?

Central Asia’s energy and water resources were once run from Moscow. In summer upstream republics such as Tajikistan and neighbouring Kyrgyzstan released water from their dams to generate electricity and help irrigate downstream republics, such as Uzbekistan. So Tajikistan already boasts the world’s highest dam, the 300-metre Nurek, built in the 1970s. In winter Uzbekistan delivered gas. That deal broke down after independence. Mr Rakhmon and Uzbekistan’s Islam Karimov do not get along. It is the custom among autocrats in these parts.

Uzbekistan thinks Rogun would parch its cotton crop and give Tajikistan political leverage. In protest, Uzbekistan has halted gas sales to Tajikistan and blocked shipments of construction materials for Rogun. Mr Karimov has warned the dispute could lead to war.

Into this morass has waded the World Bank, sponsoring two three-year assessments of the project on condition that construction is suspended. When completed, probably later this year, the studies are expected to judge the project itself feasible, but to present nine other options—of differing heights and turbine capacities—that may offer better value.

But questioning the dam’s height does not go down well with Mr Rakhmon. In 2004 Russia offered to get RusAL, an aluminium giant, to build Rogun. But after RusAL said the dam should be 50 metres lower (and perhaps tried to muscle into TALCO), the president told them to leave.

Mr Rakhmon deals in superlatives. He has built the world’s tallest flagpole and is soon to open its biggest teahouse. Yet teachers can go unpaid for months. In early 2010 he forced most Tajiks to supply cash for Rogun. Teachers earning $30-40 a month had to pay half their salaries for Rogun shares, and students had to buy them in order to sit exams.

Even if the dam is built, getting electricity out of Tajikistan will be difficult. Along with neighbouring Kyrgyzstan, it is seeking international backers for a $1 billion power line to South Asia. It does not need Rogun to operate, but the new dam would greatly enhance its appeal.

Tajikistan has other urgent concerns, too. Nurek, which provides 70% of the country’s electricity, desperately needs maintenance. Just clearing out the silt and rehabilitating the ageing plant would cost about $1 billion. Because energy tariffs are subsidised to stave off social discontent, the state electricity monopoly is broke.

Tajikistan cannot build Rogun alone. A brain drain has left it woefully ill-equipped to handle such a project. One of Rogun’s chief engineers, asked to confirm a few statistics, consults Wikipedia. The only realistic patrons for the project are outsiders who might be able to stomach the corruption, such as Russia or China. But neither wants to anger Uzbekistan, Central Asia’s most populous country, with its largest army. If only Mr Rakhmon could settle for something less than the tallest. Then he could keep the lights on in winter.