The forts and temples of the ancient Buddhist town at Mes Aynak in Afghanistan throng with the biggest crowds they have seen in more than 14 centuries. Nearby, rows of sheet metal housing built for Chinese miners are almost empty.

Hundreds of archaeologists are working at the site to excavate gilded statues of the Buddha, elaborate stupas that rise from ornately carved floors and delicate frescoes protected by centuries of mud and forgetfulness. The rich vein of copper that once funded Mes Aynak's creation is now likely to bring about its destruction: a Chinese state-owned mining company paid $3bn (£1.9bn) for the extraction rights, and the site will eventually become the world's biggest copper mine.

But while the fevered excavations are a thrilling sight for those racing to save the last traces of Mes Aynak, the lack of activity in the mining camp is alarming financial mandarins in Kabul, who are counting on mining revenue to make up for slowing streams of western aid.

This year was supposed to see production of the first copper from the site since Afghanistan embraced Islam, the first gush of ore eventually forecast to bring $300m to the government each year, and a $1bn annual boost to the still feeble Afghan economy.

Instead, the only excavation on the site is of archaeological treasures and even the most optimistic officials and analysts admit it will be two years before Mes Aynak copper is trucked off to a Pakistani port.

However, others think 2016 or 2017 are more realistic, after a series of setbacks. The Chinese camp was evacuated last summer after a Taliban rocket attack and shows no signs of being restaffed, the ministry of mines wants to renegotiate the multibillion-dollar contract for the site, and the archaeological dig that must be completed before mining starts is still in full swing.

"Don't worry, you will have at least until 2014," one of the few Chinese miners who stayed on told archaeologists earlier this year. Others from China Metallurgical Group (MCC), the company with a majority stake in the mine, had a similar message. "The cultural artefacts are the most important thing," they told surprised workers on an impromptu tour of the dig site.

Nearby, mining equipment sits idle, and many of the watchtowers ringing the core of the mine are empty at midday, although there is an outer circle of guards from a special resources protection unit.

Such concern for another country's cultural heritage, unusual for a hard-nosed Chinese natural resources company, comes as Afghanistan braces itself for huge political and security upheaval in 2014. The last Nato troops will leave by the end of the year, and the country must hold a presidential election to replace Hamid Karzai, who has ruled for more than a decade but is barred by the constitution from standing again.

Any company looking at a decades-long project might prefer to wait for more clarity on who will rule the country, and how secure it will be, before starting work in earnest, although MCC did not respond to requests for comment on its plans for Mes Aynak.

The Afghan government may also be willing to swallow some delays as it looks to renegotiate a contract that has been shadowed by corruption allegations since it was signed off six years ago. The minister who agreed it resigned shortly after reports surfaced that he had pocketed a $30m bribe from MCC, which he strongly denied. .

"We have requested for the renegotiation [of the contract]," said the current minister of mines, Wahidullah Shahrani, who has led a high-profile campaign to modernise the ministry and make its bidding process professional and transparent.

He declined to go into details on what changes he was seeking, saying only that the contract was several years old. "When it comes to these types of big projects, there could be a need for some type of what we call correction measures to be taken. But as of now we have not launched any formal renegotiation with them," he said, in an office lined with samples of the country's many valuable rocks, from lapis lazuli to iron ore.

The Chinese company was due to submit a new work schedule at the end of April, Shahrani said, and if work goes smoothly he believes production could start by 2015.

The cash is certainly needed, with World Bank forecasts for a $7bn hole in Afghanistan's annual budget after 2014, and the wider economy also suffering as US and Nato contracts dry up.

"When Aynak reaches full production the revenues to the government would be at least $300m … although it depends on fluctuations in the international copper market," Shahrani said. "In terms of its contribution to the national economy, the indirect contribution, it would be around $1bn."

But mining experts say that even if preparation work were to start in earnest this June, when the archaeologists' permission to dig ends, production is unlikely before 2016, given the preparation work usually needed for big mining projects.

"Big mines take on average between three to five years to build and construct," said a World Bank mining specialist, Michael Stanley, who declined to comment directly on Mes Aynak.

However, as long as the project is not called off, the wider Afghan economy will benefit from trucking, construction and any other work MCC contracts out, long before copper sales bring the government cash to balance its books.

"What everyone tends to forget is that the construction period for a mine, in terms of economic stimulus, is as important or more for the local economy than the production period," Stanley said.