Iltaf Shah doesn't feel welcome when he crosses the border into Afghanistan.
The Pakistani engineer works at a construction site in the Afghan border town of Wesh, building a new border post and passport office. It's not a popular project among Afghans, who say the office is located in the wrong place. Most people around here, and in a surprising number of places elsewhere in Afghanistan, believe the real border lies hundreds of kilometres southeast, deep inside Pakistan.
"You get uneducated people here saying, 'You're from Pakistan, what are you doing here?' " said the 34-year-old engineer, sitting on the floor of the half-built structure, eating a simple lunch of yogurt, lamb and flatbread.
More violent disagreements are increasingly common on these barren plains. When night falls, the French soldiers stationed near Wesh sometimes hear the crackle of gunfire as border guards take shots at each other. None of the skirmishes has erupted into full-blown warfare, but there's palpable tension along the 2,450-kilometre line, which snakes through this dry region of flatlands and mountains.
It's known as the Durand Line, named after Sir Mortimer Durand, the foreign secretary for India's British colonial government who negotiated with Afghanistan and established the border in 1893. Pakistan says it inherited the border after partition from India, but Afghanistan never formally recognized the demarcation. Most Afghans believe that the Durand agreement was only valid for 100 years, with an understanding that they would take back some territory after 1993.
Any mention of the word Durand -- among the young professionals of Kabul, on the dusty streets of Kandahar or inside the claptrap town of Wesh -- inspires strong emotions. The name evokes everything Afghans hate about Pakistan -- the Islamic insurgents who hide in Pakistan's tribal areas and launch attacks across the border, Pakistan's dominance of the Afghan economy and the alleged role of Pakistan's intelligence services in fuelling two decades of civil war in Afghanistan.
Now that Afghans have found peace with each other, it seems they're also rediscovering their nationalism and old hatreds. While it may seem remarkable that a weak and broken country would pick a fight with a nuclear power and major trading partner, some observers expect the border question to become an explosive issue in the new Afghan parliament.
"It could translate into some big problems. This is the giant pink elephant in the room that nobody wants to talk about," said a Western expert, who asked for anonymity because his organization operates on both sides of the border and hasn't declared a position on what he described as an "extremely sensitive" topic.
Hamid Karzai, Afghanistan's President, has also avoided the question. Observers say he's treading carefully because ordinary Afghans are clamouring for action but the government remains incapable, and unwilling, to do anything as long as Afghanistan remains dependent on foreign assistance.
But that caution extends only so far. Last week, Afghanistan firmly rejected Pakistan's proposal to fence the border, declaring that the demarcation question must be settled first.
Pakistan, meanwhile, has taken other steps to reinforce its claims. Four years ago in Wesh, Pakistanis built a hulking, three-storey brick gateway to mark the border several kilometres inside what Afghans thought was their territory.
In the shadow of that gate, the United States has funded construction of a new, $3.5-million Afghan border post. The Pakistani and Afghan workers on the project have very different views, however, about whether it's a good idea to fix the border's position so concretely.
"As our government becomes stable, Pakistan is worried we will start demanding the Durand agreement," said Marajudin, 34, the site's doctor, who like many Afghans uses only one name. "Everybody know this land belongs to Afghanistan."
The Pakistani engineer, Mr. Shah, shook his head. As an ethnic Pashtun he feels kinship with the people on the Afghan side of the border, he said, but that doesn't mean he wants to join Afghanistan.
"The doctor is saying, 'Join us. We speak the same language we have the same traditions,' " he said. "We say 'No. Simply no.' Afghanistan has nothing except weapons. We want peace and freedom."
Some Afghans say they're willing to fight for the territory. Lagwar, 55, a grizzled former military commander in the southern city of Kandahar, clapped his hands with joy when informed that a journalist would write about the Durand Line.
"If there is one drop of blood in my veins, this is my wish: to capture the Durand Line again," he said.
Even among the moderate, educated elite in Kabul, the border grievance runs deep.
Baqir Hassan Zada, 25, an accountant who speaks five languages, looked up from a game of cards in the city's central park and scowled when asked whether his country would ever find a lasting peace after so many years of war.
"Not until we deal with Pakistan," Mr. Zada said. "For many years, Pakistan has been cheating us. Now they're scared of what will happen when we have a strong country."