THE dollar used to be the universal tourist currency, accepted almost anywhere, from the streets of Hanoi to the plains of Africa. But the continued slide of the dollar against other currencies has led the greenback to be shunned in unexpected places, creating new problems for American travelers and pushing prices higher.

The Taj Mahal has stopped accepting dollars for the entrance fee, under a new edict from the Indian Ministry of Culture that also affects other national tourist sites like the 13th-century minaret known as the Qutb Minar and Humayun’s Tomb in Delhi. As a result, for entrance to the Taj Mahal, Americans must now pay 750 rupees, about $19, at the rate of 39 rupees to the dollar, compared with $15 previously.

Some tour operators say they have encountered newfound resistance to dollars in parts of Vietnam and Peru, especially in villages that are off the beaten path.

“It used to be a $100 bill was universal everywhere, from Moscow to Mozambique,” said Peter Rudy, the North America director for KE Adventure Travel, a Denver-based outfit that books adventure trips throughout the world. “It’s not now.”