Two weeks ago, Indian military officials announced that they had discovered that a platoon of Chinese soldiers had crossed the de facto border between the two countries and set up camp an unprecedented six miles inside Indian-claimed territory, sparking a still-unresolved standoff.

China’s Foreign Ministry said last week that its troops were patrolling on the Chinese side of the border and “never trespassed the line.”

Such disputes have a long history. But the latest incident, in a previously uncontested area, involves the most serious accusations by India in 25 years and is posing a challenge for the countries’ diplomats ahead of a visit to New Delhi by China’s new premier, Li Keqiang, this month.

New Delhi and Beijing have indicated that they do not want the border disagreement to derail their broader relationship.

Indian officials at first underplayed the alleged incursion. Prime Minister Manmohan Singh called it a “localized” problem and said his government did not want to “accentuate” it. Foreign Minister Salman Khurshid described the dispute as an “acne” that could be addressed “by simply applying an ointment.”

Chinese Foreign Ministry spokeswoman Hua Chunying said Beijing believes peace in the border areas serves both countries’ interests. “The border issue is an issue left over from history,” she said in a statement, adding that “both sides should carry out communication and negotiations” to resolve it.

But as the standoff in the mountainous northern region of Ladakh entered its 16th day Thursday, such resolution appeared as distant as ever. Three meetings between army officials on the border and diplomatic exchanges have failed to budge the two sides from their sticking points: New Delhi wants the Chinese troops to step back from the face-off point and remove their tents. Beijing insists that the troops, who remain in the camp, are on the Chinese side of the Line of Actual Control.

Complicating diplomatic efforts is the pressure of two impending official visits: In addition to Li’s scheduled trip to India, Khurshid is expected to travel to Beijing next week.

“Diplomacy requires time and space,” Indian Foreign Ministry spokesman Syed Akbaruddin said Thursday.

India is examining what it can do — including limited, tactical measures on the ground and possibly calling off Khurshid’s visit — without jeopardizing ties. On Wednesday, even as its top security panel discussed military options, it announced that it will stage counterterrorism military exercises with China later this year. Senior army officers also attended May Day celebrations in China.

The neighbors have held 15 rounds of fruitless border talks since the 1990s. Ties have frayed several times as the two sparred over the construction of dams by China on rivers that flow into India or visits by Indian officials to border provinces that China claims. India has also watched warily as China has built military infrastructure and road and rail networks near the border in Tibet.

Many Indians have interpreted the New Delhi government’s caution in the latest incident as weakness, even cowardice. But some see it as a sign of maturity.

“Only if our foreign minister goes to Beijing will we have clarity on what the Chinese concerns are,” said Alka Acharya, a professor of Chinese studies at Jawaharlal Nehru University in New Delhi. “They say we have built some structures in that disputed area. There are conflicting claims. We can’t keep beating our chests and shouting, ‘Throw them out.’ ”