BRUSSELS -- Afghan President Ashraf Ghani appealed Wednesday for sustained international help for his insurgency-wracked country, promising international donors that the government would concentrate its future efforts on tackling rampant poverty.

"We are going to be relentlessly focused on reduction and elimination of poverty as our central task," Ghani told representatives from more than 70 nations and dozens of agencies and non-governmental organizations gathered in Brussels to try to drum up billions of dollars to keep the Afghan government afloat.

The Afghan government is estimated to only be capable of meeting 20 per cent of its budget, and Ghani noted that 39 per cent of the Afghan population lives on less than $1.35 a day.

But donor fatigue has grown over the 15 years of international efforts in Afghanistan since a U.S.-led coalition ousted the Taliban for harbouring former al-Qaida leader Osama bin Laden. The European Union, hosting the conference, has been struggling to raise around $3 billion that Kabul will need each year. The last donor conference, in Tokyo in 2012, secured $4 billion in annual subsidies for development.

The Taliban have proved tenacious, waging an increasingly powerful insurgency around the country. Afghan forces battled Taliban fighters in the northern city of Kunduz for the third straight day on Wednesday and American helicopters provided air support to troops on the ground in the wake of the multipronged attack on the city launched by insurgents this week.

Despite the setbacks, and rampant corruption, U.N. Secretary General Ban Ki-moon said that "it's important today that the international community sends a strong message of support."

Afghanistan's leaders "have been making impressive reforms and development plans to change the lives of people that have been suffering too long," Ban said.

Acknowledging the many setbacks that Afghanistan has faced, U.S. Secretary of State John Kerry said that he still has "an enormous sense of confidence about the future."

"Year by year our shared effort, one of the largest international coalitions ever assembled, and maintained over a sustained period in time, is in fact yielding encouraging dividends," Kerry told the representatives.

The EU's foreign policy chief, Federica Mogherini, said the EU and its member states will pledge 1.2 billion euros ($1.3 billion) each year up until 2020 "and we would expect a similar level of engagement from our partners."

"We all need to commit to a new deal for Afghanistan," Mogherini said as she opened the meeting.

But many participants at the conference have heard such rhetoric before, and some were underwhelmed by the promises being made.

"The commitments to fighting corruption are very weak and we are disappointed," Ikram Afzali, from the anti-corruption civil society group Integrity Watch Afghanistan, told The Associated Press.

He said that some of the anti-corruption plans on the table are "just window-dressing for this conference."

Other plans are to be drawn up for next year. "We don't have time," he said.

In earlier comments to reporters, Mogherini denied reports the bloc is making aid conditional on Afghanistan taking back people who have fled to Europe, saying there is "never a link between our development aid and what we do on migration."

But there is clear pressure on the authorities in Kabul to do more to stop people fleeing and take back those who leave.

The head of the International Organization for Migration, William Lacy Swing, told the AP that around 6,000 people are flooding back into Afghanistan from Pakistan and Iran every day, and that any increased returns from Europe would put additional pressure on the country's fragile institutions.

"This is a very vulnerable society with very limited capacity to receive these people, in terms of health facilities, education facilities and training facilities," Swing said.

"We need to do a lot more to help those who have departed already, to help these people find a new life," he added.

Afghanistan has been mired in conflict for decades. At the height of the 15-year U.S. and NATO intervention, billions of dollars flowed into the country, creating a false economy with double-digit growth. But the drawdown of troops in 2014 led many aid workers and international agencies to depart or scale back their operations, causing the economy to all but collapse.

Officials estimate up to 50 per cent unemployment. Deteriorating security deters foreign investment in key fields such as mining and infrastructure, and drives the country's youth onto the migrant trail to Europe in search of opportunities.

Outside EU headquarters in Brussels, hundreds of people from Afghanistan's Hazara community rallied to denounce discrimination against them.

Lynne O'Donnell in Kabul contributed