Afghanistan's leaders will head to Brussels this week, seeking billions of dollars in aid as the country confronts an increasingly powerful Taliban insurgency and pervasive corruption.

President Ashraf Ghani and Chief Executive Abdullah Abdullah hope to secure pledges totaling about $3 billion a year at the conference, which will be held on Tuesday and Wednesday. Afghanistan already receives about $5 billion a year, mostly from the United States, to cover defense costs. The last donor conference, in Tokyo in 2012, secured $4 billion in annual subsidies for development.

Afghanistan has been mired in war 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 growth in the double-digits. 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 percent 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. Ghani will nevertheless argue that progress has been made since Tokyo regarding corruption and judicial and electoral reform.

"Afghanistan is no longer just receiving a blank check, this time we have to make sure the support we are receiving goes to the right places, in the right hands, and there is mutual accountability on both sides, Afghanistan and the donors," said Javid Faisal, a spokesman for Abdullah.

Afghanistan's illicit production of poppies for heroin, worth about $3 billion a year, has served as a cash cow for the insurgents and spawned a corruption epidemic. The anti-corruption group Transparency International consistently ranks Afghanistan among the top three most corrupt countries, alongside Somalia and North Korea.

"Corruption used to be a shame in this county, but now all the things it brings are a badge of pride," said analyst Haroun Mir, referring to officials who flaunt expensive watches and cars, and live in huge marble houses known as "poppy palaces" despite receiving official salaries of a few thousand dollars a month.

The average income for Afghanistan's estimated 30 million people, most of whom are illiterate farmers, is less than $1,000 a year.

Speaking in Washington last week, U.S. Special Representative for Afghanistan and Pakistan Richard Olson said Afghanistan relies on donors for around 70 percent of its budget. He said international donors in Brussels are expected to pledge $3 billion a year in development funds through 2020.

He insisted progress has been made since 2012, with government revenue collection growing last year by 20 percent to around $1.8 billion, improved regulations against money laundering and a reduction in illegal procurements for defense and police.

"Much remains to be done on the anti-corruption agenda, but the government is making headway. More than 600 judges, 20 percent of prosecutors, and 25 percent of customs officials, who were either unqualified or corrupt, have been removed from their positions over the past year," Olson said.

Despite the incremental improvements, however, corruption remains one of Afghanistan's most intransigent problems, and is regularly cited by ordinary people in opinion polls as one of their main concerns, along with security.

In a report published last month, John Sopko, the U.S. official in charge of monitoring reconstruction, said that over the last 15 years corruption "grew so pervasive that it ultimately threatened the security and reconstruction mission in Afghanistan." Sopko said the Afghan body charged with leading anti-corruption efforts was ineffective in getting officials to declare assets.

Afghanistan's own Independent Joint Anti-Corruption Monitoring and Evaluation Committee has criticized the government for not offering enough on anti-corruption in its framework for Brussels. It called for specifics on tackling corruption in investment, asset registration by officials, civil service and justice reform, and the country's "deeply compromised" mining sector.

The Taliban also noted the corrupting impact of the donors' cash contribution since they were pushed from power in 2001, saying aid money had failed to bring "any meaningful change into the lives of the ordinary citizens."

The conference, co-hosted by Kabul and the European Union, will be attended by over 70 nations and 30 international agencies and non-government organizations. U.S. Secretary of State John Kerry and the U.N. Secretary-General Ban Ki-moon are also due to attend.