Beijing, Oct 9 Two days after Indian Defence Minister Nirmala Sitharaman visited Nathu La, China on Monday said the Sikkim section of the India-China border has been delineated by historical convention and asked New Delhi to abide by this "fact". "The Sikkim section of China-India border has been delineated by the historical convention and the Nathu La pass is the best witness to that fact," Chinese Foreign Ministry spokesperson Hua Chunying said, referring to the 1890 treaty between Britain and China. China repeatedly invoked this treaty to assert its claim over Doklam during the 73-day military stand-off with India in the Sikkim section of the border. "We hope that India could abide by this fact, observe these historical conventions and agreements and work with China to maintain peace and tranquility at the border," Hua said. She was responding to question about the visit by Sitharaman to an Indian Army post in Nathu La. The Nathu La pass separates India from China's Tibet. The first visit to the area by India's newly appointed Defence Minister created a buzz when she interacted with Chinese troops across the border and taught them how to say "Namastey" - hello in Hindi.