Nuon Chea said he wanted to see original documentation and hear recordings of his own voice before giving the accusations credence.
In it are dozens of photographs from a 1978 trip Becker took with other journalists at the invitation of Khmer Rouge leaders.
The aid came “without conditions” and was not expected to be reimbursed, he said under questioning from a court prosecutor.
Becker’s book relies in part on her early reporting on the Khmer Rouge and interviews with its leaders, including Pol Pot.
Meanwhile, two suspects in those cases told VOA Khmer this week they would be relieved to have the cases dropped.
The court is currently trying three more top leaders of the regime, but many critics say this is as far as the hybrid court will go.
Kaing Kek Iev, better known as Duch, had appealed to reduce his 35-year-term.
Duch, who is 69, was handed a commuted sentence of 19 years at the end of his atrocity crimes trial in 2010.
Defense attorneys for three jailed regime leaders have challenged the authenticity of documents from the well-established organization.
Nil Nonn, head judge of the Trial Chamber, stopped him and reminded him to keep his questions limited to the case at hand—No. 002.
Bou Meng and Chhum Mey spend less time at the trial of Khmer Rouge leaders these days, and more time at the torture center they both survived.
The UN sent its expert for the court to Cambodia this week to meet with government and court officials over a UN-appointed judge.