WASHINGTON: The United States on Tuesday called on Afghans to refrain from speculation on their presidential election, voicing hope for a transparent process to assess fraud allegations.

Early results put President Hamid Karzai neck-and-neck with former foreign minister Abdullah Abdullah, who has accused the incumbent of rampant fraud but also appealed for calm.

"We call on all parties to refrain from speculation until the national results are announced," State Department spokesman Ian Kelly told reporters.

"We all need to be patient, allow the respective authorities to do their jobs thoroughly and we have to wait for the results to be released," he said.

Kelly said the United States took fraud allegations "very seriously" but said Afghan authorities also promised to probe charges of wrongdoing.

"We want to see this process play out. An important part of that process will be an open and transparent investigation" of fraud allegations, he said.

He reiterated that the United States was neutral in Afghanistan's second presidential election.

Karzai has led Afghanistan since the aftermath of the US-led military campaign that ousted the extremist Taliban regime in 2001 and enjoyed a warm relationship with former US president George W. Bush.

President Barack Obama, who has made Afghanistan and neighboring Pakistan a key foreign policy priority, is widely seen as cooler to Karzai.