AFP reports citing a US diplomat.
The United States and other countries have said the discovery of the weapons on the Chong Chon Gang freighter is probably a breach of UN sanctions against North Korea.
North Korea and Cuba have said the shipment consists only of obsolete missiles and other weapons parts from the mid-20th century being sent to North Korea for repairs.
The vessel set out from Cuba and was trying to enter the Panama Canal when it was stopped by an anti-narcotics patrol, which later found the weapons concealed beneath several tonnes of sugar.
"We understand that the group (of UN sanctions experts) will be visiting Panama very soon and will start the investigation," Jeffrey DeLaurentis, a deputy US ambassador to the United Nations, told reporters.
Panamanian Public Security Minister Jose Mulino said the team was scheduled to arrive August 5.
The United States is the current president of the UN Security Council.
North Korea faces several rounds of sanctions over its nuclear weapons program, which are monitored by a Security Council committee currently chaired by Luxembourg.
"The United States commends the actions of Panama in bringing this swiftly to the committee. Efforts are ongoing to determine the contents of the vessel," said DeLaurentis.