Backers of Laotian general Vang Pao appealed to US President Barack Obama to let him be buried with honors at Arlington National Cemetery, after the US military rejected their request.

The call came on the second day of a traditional six-day funeral for the 81-year-old general -- who led a CIA-backed "secret army" helping the US during the Vietnam war -- in Fresno, California, where he died last month.

Thousands of ethnic Hmong from the US and overseas have gathered to pay their last respects, but ceremonies have been clouded by the decision to refuse Vang Pao an Arlington burial, announced as the funeral started Friday.

"We were very disappointed to hear that the request for the burial of General Vang Pao has been denied," said the Memorial Central Committee organizing the Hmong veteran's funeral.

"We hope President Obama and the defense secretary will allow a burial waiver for General Vang Pao," it added in a statement issued on behalf of "Vang Pao’s family, Hmong Americans, Vietnam war veterans and friends."

Charlie Waters, a friend of the late general, said that Senator John McCain, a Vietnam veteran himself, would see Vice-President Joe Biden on Monday to press him on Vang Pao's case.

"We're not buying the idea that Arlington is becoming full. There's space for a hero," said Korean war veteran Waters, adding that he would offer to give his own place in Arlington to Vang Pao.

Vang Pao led the Central Intelligence Agency-backed force that assisted the United States in Vietnam, during its ill-fated war with communist forces in the north of southeast Asian nation.

He died of pneumonia on January 6 in Fresno, one of the major hubs of the 250,000-strong Hmong community living in the United States, some 30-40,000 of whom live in the west coast state of California.

His family and supporters had applied to the US military for a waiver to allow Vang Pao to be buried at Arlington, normally reserved for American veterans.

On Friday the Pentagon said the family's Arlington request "was thoroughly reviewed by a board comprised of senior military and civilian officials" but it "unanimously recommended denial of the request for exception to policy."

But the memorial committee said general Vang Pao served the United States valiantly. "His exceptional service symbolizes the death of each soldier," the statement said.

"We strongly believe the right thing to do is to honor his contributions to the United States. He fought to protect America’s freedom, democracy, and justice."

It cited precedents including Iraqi Air Force captain Ali Hussam, killed in the Iraq war. "There are many others. General Vang Pao has contributed directly to the US military and deserves to be laid to rest at Arlington," it said.

One of Vang Pao's sons, 46-year-old Chai Vang, said he believed the Arlington decision could be reversed.

"As far as the family, we're really upset. He put his life and all of his efforts towards democracy in Laos," he told AFP before the appeal was issued, adding: "Anything can be reversed.

Vang Pao, a fierce opponent of the communist government in Vientiane, was also a controversial figure.

In 2007, he was arrested in California on charges of plotting to overthrow a foreign government after an undercover agent tried to sell him weapons at a Thai restaurant.

Prosecutors dropped their charges in 2009. A judge later ended the case for the remaining 11 Hmong Americans accused in the case amid persistent questions over the government's evidence.