Afghanistan on Sunday postponed parliamentary elections until September due to a lack of funding from donor nations after widespread fraud in last year's presidential poll.

The announcement came as President Hamid Karzai left for Turkey, the start of a tour that will include Berlin and London. Karzai will appeal for financial and other support for his government.

Another flawed election would erode support for Karzai's government at a time when he has pledged to battle corruption and improve services.

The Independent Election Commission has said it needed about $50 million from the international community to pay for the parliamentary election, budgeted to cost $120 million.

That money has not come through in time to hold the vote as planned on May 22, according to commissioner Fazel Ahmed Manawi. He also attributed the delay to security concerns, logistical challenges and the need to improve the election process at a news conference to announce the decision.

The vote will be held on Sept. 18 instead, Manawi said.

"There is no doubt that we are faced with different kinds of problems, but the major problem in our way is the lack of budget funds and security concerns," he said.

The U.S. Embassy in Kabul said it respected the decision and would continue to work with the Afghan government "to pursue election reform for the upcoming parliamentary elections and for the long term."

Manawi said the international community has not refused to help pay for the vote but is studying the request.

U.S. lawmakers and other critics had pressed for a postponement in the wake of last August's disputed poll that re-elected Karzai, warning that holding the vote without substantive electoral reform could undermine support for U.S. aid to the insurgency-wracked country.

Chief U.N. envoy Kai Eide also said earlier this month that there is a provision in Afghan law that permits the elections to be postponed for a few months.

Karzai had insisted the constitution, which specifies the elections be held by May, must be observed.

But Manawi said Sunday that a review of the constitution and the electoral law paved the way for the postponement.

The August presidential vote was so tarnished that U.N.-backed fraud investigators threw out more than a million ballots — enough to force Karzai into a second-round vote. The runoff was later canceled when Karzai's top challenger, former Foreign Minister Abdullah Abdullah, dropped out, saying he was not confident the vote would be fair.

Some nations also were concerned that having to guard polling stations in May would be a distraction for the 37,000 U.S. and NATO reinforcements being deployed with orders to stall the Taliban's momentum.

Two U.S. service members were killed Sunday in a bombing in southern Afghanistan — the second strike to kill American troops in as many days in the area, which is expected to be the main focus of a U.S. troop surge.

Gen. Stanley McChrystal, the top NATO commander in Afghanistan, has warned the risk to foreign troops will increase along with the influx, which is aimed at stabilizing the country.

At least 24 American deaths have been reported so far this month — compared with 14 for the whole of January last year.

A suicide bomber in southern Helmand province also targeted U.S. troops in a market Saturday, killing two Afghan children, officials said. NATO would not specify if it was the same attack that killed the two Americans, pending notification of their families.

Helmand government spokesman Daoud Ahmadi said the bomber was targeting U.S. troops on a foot patrol and three civilians also were wounded in the attack in the Khan Neshin district.

NATO said in a statement that the two civilians killed were children.

Karzai planned to meet with Pakistani President Asif Ali Zardari as well as Turkish officials during his visit to Turkey. He was then to travel to Berlin on Tuesday to meet with German Chancellor Angela Merkel and leading lawmakers before heading to London for conference Thursday, when international and Afghan officials will discuss ways of shoring up the government in Kabul.