Madonna and her husband, film director Guy Ritchie, took custody of David, then 14 months old, last October. His father had placed David in an orphanage.
Malawi's Child Welfare Services is expected to file a report on the couple's suitability as adoptive parents after two trips to their London residence this year. But welfare services has already missed one visit, which was set for May.
Director Penston Kilembe, who is overseeing the case, indicated in an interview this week that money is an issue. He said hopes to go to London by month's end.
"We have been unable to travel because of logistical problems," Kilembe said. "You know it requires some resources for me to travel."
Malawian law is fuzzy on foreign adoptions. Regulations only stipulate that prospective parents undergo an 18- to 24-month assessment period, a rule that was bent when Madonna and Ritchie were allowed to take David home.
Lawyer Justin Dzonzi is chairman of a coalition of 67 children's and human rights organizations that raised the lack of regulations in their successful lawsuit to become party to overseeing David's adoption.
Dzonzi said it was unrealistic to expect Malawi to oversee the adoption without help, possibly from British child welfare authorities.
"We just don't have the resources and the expertise," Dzonzi said.
International adoption and children's rights groups have said the lack of clarity in Malawi's law could make the southern African country's children vulnerable to trafficking.
"We have reservations" about Malawi's ability to oversee the Madonna adoption on its own, said Maxwell Matewere of Eye of the Child, which is part of the Human Rights Consultative Committee. "We are a little worried whether Kilembe is competent enough to assess the U.K. environment and to make a fair conclusion on the whole process."
Kilembe said his job is straightforward.
"What we expect is the child must be provided all the necessities of basic needs for him to grow up. He must go to school, must socialize, he must be taken care of, must have a ... comprehensive medical cover so that he is able to be protected."
Madonna's celebrity makes David's prospective family different from most.
Stevan Whitehead, chairman of the Overseas Adoption Support and Information Service, a private British group, said David was in the spotlight when he was first brought to London, where photographers and TV cameras met him at the airport.
"Frankly, I blame the media for that, I don't blame his mother. And since then she's done a very good job to keep him out of the spotlight," Whitehead said. "If he is kept out of the media, I can't see any significant difference between being brought up by a pop star or anybody else."
David's father said he was happy to have the adoption go ahead as long as David is well looked after.
"Yes, I miss him," he added.