China has said that "the atmosphere is not right" for a formal or bilateral meeting between Prime Minister Narendra Modi and Chinese President Xi Jinping when they gather for the G20 summit in Hamburg.

The statement comes as the armies of both countries are caught in a lengthy stand-off at the border near Sikkim.

PM Modi arrived in Hamburg last night for a conclave of the G20 group of nations. Both he and the Chinese president will hold bilateral meetings with other leaders at the summit.

Sources in the Indian government said they're not sure of whether an informal one-on-one meeting for PM Modi and President Xi will take place.

The leaders will be part of a smaller session of BRICS -Brazil, Russia, India, China and South Africa - that will meet on the sidelines of the main C20 summit that collates the leading industrialised and emerging economies.

China has this week issued a series of warnings to India -some through state-run newspapers - about the urgent need for New Delhi to withdraw its troops from an area that Beijing claims as its own near Sikkim. Indian soldiers arrived at the area early in June to stop the construction of a road that New Delhi holds as "a serious security concern."

China says the Indian Army's actions violate an 1890 border agreement between Britain and China that previous Indian governments have pledged to uphold and that it will not move for any dialogue till Indian troops are pulled back.