(Reuters) - Western embassies and the United Nations are urging Pakistan to incorporate into its plan to deport hundreds of thousands of undocumented migrants a way to identify and protect Afghans who face the risk of persecution at home, officials told Reuters.

Pakistan has set Nov.1 for the start of the expulsions, which could leave more than 1.7 million Afghans vulnerable in the South Asian nation, of a total of more than 4 million migrants and refugees from its neighbour.

"We are asking the government to come up with a comprehensive system and ... mechanism to manage and register people at immediate risk of persecution if forced to return," Qaiser Khan Afridi, the spokesman for the U.N. refugee agency in Pakistan, told Reuters.

"Because they cannot return, they can't go back to Afghanistan because their freedom or their life might be at risk."

Spokespersons for Pakistan's interior and foreign ministries did not immediately respond to a request for comment.

It was not immediately clear if Pakistan had agreed to take up the proposals by the United Nations and other embassies.

Afridi added that if Pakistan approved, his agency, the United Nations High Commission for Refugees (UNHCR), had offered to provide it the technical assistance and financial support needed for the effort.

Two official sources said several embassies of NATO members in Islamabad were lobbying Pakistan's government at the highest levels, along with UNHCR, seeking exemption from deportation for thousands of Afghans being resettled to Western countries.

"To help protect vulnerable individuals, we have shared a list with the government of more than 25,000 Afghan individuals in the U.S. resettlement and relocation pipelines," a senior U.S. official told Reuters.

The official, who spoke on condition of anonymity as the matter is sensitive, added that U.S. authorities were working to issue letters to such individuals identifying them as being part of the resettlement efforts.

The official sources, who sought anonymity, said they continued to call for the setting-up of a "protective screening mechanism" for those being deported.

That would probably involve an interview to evaluate a potential deportee's claims about fear of persecution and decide the need for additional protection, in line with international humanitarian law, officials familiar with the proposals said.

About 600,000 Afghans have crossed into Pakistan since the Taliban took over in 2021, in addition to a large number present since the Soviet invasion of 1979.

This month, Pakistan said it would deport all foreigners without proper documents after Wednesday, and about 60,000 Afghans returned home in October, with more expected to do so.

Pakistan says Afghan nationals have been found to be involved in crimes and militancy, and are a drain on its resources.