Afghanistan would become a "pariah state" if the Taliban take control by force, US Secretary of State Antony Blinken said on Wednesday, as a top-level delegation from the insurgent group visited China to assure officials of their international obligations.

"An Afghanistan that does not respect the rights of its people, an Afghanistan that commits atrocities against its own people would become a pariah state," Blinken told reporters in India, where he is on his first official visit.

In China, the Taliban’s leadership assured Beijing the group will not allow Afghanistan to be used as a base for plotting against another country.

A delegation including co-founder Mullah Abdul Ghani Baradar is in China for talks as the insurgents continue a sweeping offensive across Afghanistan, including areas along their shared border.

Their frontier is just 76 kilometres long, and at a rugged high altitude without a road crossing, but Beijing fears Afghanistan could be used as a staging ground for Uyghur separatists in Xinjiang.

Taliban spokesman Mohammad Naeem told AFP those concerns were unfounded.

"The Islamic Emirate assured China that Afghanistan’s soil would not be used against any country’s security.”

"They [China] promised not to interfere in Afghanistan’s affairs, but instead help to solve problems and bring peace.”

Beijing confirmed the thrust of the talks, which were led on the Chinese side by Foreign Minister Wang Yi.

But in Kabul Afghanistan’s President Ashraf Ghani urged the international community "to review the narrative of the willingness of the Taliban and their supporters on embracing a political solution”.

"In terms of scale, scope and timing, we are facing an invasion that is unprecedented in the last 30 years,” he warned in a speech on Wednesday.

"These are not the Taliban of the 20th century... but the manifestation of the nexus between transnational terrorist networks and transnational criminal organisations.”

In New Delhi, Blinken warned the Taliban they would have to change if they wanted global acceptance.

"The Taliban says that it seeks international recognition, that it wants international support for Afghanistan. Presumably it wants its leaders to be able to travel freely in the world, sanctions lifted, etc,” he said.

"The taking over of the country by force and abusing the rights of its people is not the path to achieve those objectives.”

Analysts say China, whose stated foreign policy position is non-interference in other countries’ issues, is queasy about the religiosity of the Taliban given their proximity to Muslim-majority Xinjiang.

But the meeting gifts legitimacy to an insurgent group craving international recognition, and a potential diplomatic shield at the UN, to match their military march across the nation.

"Wang Yi pointed out, the Afghan Taliban is a crucial military and political force in Afghanistan,” Foreign Ministry spokesman Zhao Lijian told reporters in Beijing.

"China has throughout adhered to non-interference in Afghanistan’s internal affairs... Afghanistan belongs to the Afghan people,” he said, in stark contrast to the "failure of US policy towards Afghanistan”.