The Tanzanian government next year wants to kick off construction on a road that will cut through a 50-kilometre (30-mile) swathe of the Serengeti park classed as a world heritage site by the United Nations Educational, Scientific and Cultural Organisation.
Conservationists say it will have a devastating effect on the local ecology, in particular wildlife migration patterns.
"Modern economy should not by any means be at the expense of nature, or at the expense of culture," UNESCO Director-General Irina Bokova told journalists.
"I know that the pressure of modernity is very high," she said. "Countries must make a balance between preserving their heritage sites and still developing their economy."
Referring to a port project in neighbouring Kenya, Bokova said UNESCO's world heritage committee had received "assurances" that it will not affect neighbouring Lamu island, the UN-listed showcase of Swahili culture off the coast.
But she added, "The world heritage committee is following very closely the developments, and should it consider that they may endanger the site, we will immediately alert the government."
"We have such a good relationship with the government of Kenya that whatever concern we may have we can share it with the government and find a solution," Bokova said.
An intergovernmental committee started meeting Monday in Nairobi to decide whether to inscribe up to 51 cultural practices from around the world on the Convention of Intangible Cultural Heritage.
Those being submitted range from Meshrep, the harvest festival ceremony of northwest China's Turkish-speaking Muslim Uighur people, to French gastronomic cuisine, oil wrestling in Turkey's Kirkpinar region and falconry in 11 countries.
The convention, separate from the one governing sites of cultural value or great natural beauty, was first signed in 2003 and has so far been ratified by 132 countries.
Some 178 cultural practices are already protected by UNESCO.