Last year's presidential election was marred by fraud
Afghanistan is to postpone its parliamentary elections by four months until September, the country's election commission has confirmed.
Elections were to take place before 22 May under the constitution but a new date of 18 September has been set.
The commission cited a lack of funds and security concerns for the delay.
Last year's presidential election was marred by fraud, and Western nations have been pushing for reforms ahead of the parliamentary vote.
Fazil Ahmad Manawi, a senior election commissioner, told reporters in Kabul: "The Independent Election Commission, due to lack of budget, security and uncertainty and logistical challenges... has decided to conduct the [parliamentary] election on September 18, 2010."
John Simpson, BBC News, Kabul
The decision has removed a distinct irritant in the relationship between President Karzai and the Western countries which support him.
The four-month delay will give the international military force more time to improve security in southern parts where the Taliban were able to intimidate many voters in last August's presidential election. The delay will also allow more time to introduce reforms which are intended to prevent the kind of fraud widely alleged in President Karzai's re-election.
The postponement will also greatly improve the atmosphere before next Thursday's international conference on Afghanistan in London.
The commission earlier said it needed about $50m from international donors to part fund the estimated $120m election budget.
United Nations funds are available to fund the elections but have been made contingent on reforms to the system.
The US and other Western nations have said that another election marred by fraud could undermine their strategy in the country.
The chief UN envoy Kai Eide said this month that Afghan law did provide for a delay to the polls, although President Hamid Karzai had wanted the original date to be met.
One international diplomat told the Reuters news agency the postponement was "a pragmatic and sensible decision which will allow time for reform of the key electoral institutions to enable cleaner parliamentary elections".
Underlining the continuing security concerns, Nato said that three US service members were killed in two separate bomb attacks in southern Afghanistan on Sunday.
Afghanistan is also facing ongoing political uncertainty, with a number of cabinet posts still vacant following the re-election of Mr Karzai as president.
Hamid Karzai had wanted to observe the original election date
Parliament has twice rejected many of Mr Karzai's nominations for a new cabinet, forcing the president to direct deputy ministers or other caretaker figures to run their ministries.
The uncertainty comes ahead of a key conference on Afghanistan in London next week.
Improving the governance of Afghanistan will be a key issue at the conference, along with security.
Western nations will try to cement their strategy both for increased foreign troops and a strengthened Afghan force.
US envoy for Pakistan and Afghanistan Richard Holbrooke said last week the "strategy for Afghanistan is settled" and the London summit would implement it.
A panel of officials from Afghanistan, the UN and countries contributing troops recently agreed to increase the size of the Afghan National Army from the current figure of about 97,000 to 171,600 by the end of 2011.
Last year, US President Barack Obama announced a review of strategy, saying he would send 30,000 more troops to Afghanistan.
Nato allies agreed to send at least 7,000 extra troops to support the US surge.