The United Nations has cut in half a cash grant for Afghan refugees in Pakistan to return to their country, according to officials.

The reduction - from $400 to $200 - comes as a voluntary repatriation operation is set to resume on Monday, with 16,000 people based in Pakistan's Khyber-Pakhtunkhwa province registered to head home.

Under the UN refugee agency’s ( UNHCR ) scheme, as many as 370,000 registered Afghan refugees repatriated voluntarily in 2016, brining the total number of returnees to 4 milion since 2002, when the scheme began.

READ MORE: Afghan refugees return home amid Pakistan crackdown

The UNHCR last November said it would end cash support to returnees in mid-December - but the grant resumed on March 1.

Dunya Khan, a spokesperson for UNHCR in Islamabad, on Sunday said the cash cut was due to funding shortages.

"We could not sustain the amount of $400 for Afghans leaving Pakistan due to budget cuts, but the money they get will at least covers their transportation cost," Khan told Al Jazeera.

Despite the announced cuts, many Afghans continued registering - even as they expressed worries about what lies ahead for them.

"The amount before [the cut] at least helped us with our basic needs during our return to Afghanistan, but something is at least better than not having money at all,” said Ilyas, an Afghan refugee in Pakistan, who sells ice-cream in Peshawar city.

"An uncertain future awaits us," he told Al Jazeera.

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Pakistan hosts 1.3 million registered Afghan refugees, in addition to nearly a million unregistered Afghans, 600,000 of whom live in Khyber-Pakhtunkhwa in the border with Afghanistan.

In 2014, after a Tehreek-e-Taliban-claimed school attack in Peshawar killed more than 143 people, including 132 children, the Pakistani government announced a decision to deport registered and unregistered Afghans on the grounds of national security, accusing some refugees of posing a threat.

Since then, incidents of police abuse, beatings and extortion against Afghans has reportedly skyrocketed, prompting many to return to war-torn Afghanistan, according to US-based rights group Human Rights Watch.

For decades, the Pakistan-Afghan border was open to cross from either side without requiring passport or visa.

Millions of Afghans used it to seek refuge from war and violence in their country, fleeing the Soviet invasion in 1979, the Taliban's excesses in the 1990s and the 2001 US-led invasion in 2001.

Pakistan temporarily sealed the Torkham and Chaman crossings on February 16, after a string of suicide attacks on Pakistani soil that killed at least 130 people, but the crossings were reopened last month.

Pakistan shares a mountainous 2,500km-long border with Afghanistan , which the latter disputes. Previous attempts to fence or formally demarcate the border have been met with resistance from Kabul.