Secretary of State Cyrus Vance sought to justify the aid based on the importance of copper and cobalt mining. Announcements seeking to hire American mercenaries to fight in Zaire appeared in California. A man, David Bufkin, was identified as doing the recruiting. The announcements were later traced to the Central Intelligence Agency (CIA)  Belgium sent weapons to the Zaire government but declined Mobutu's request for military assistance. China sent 30 tons of weapons. France sent weapons and ammunition. The US asked for Nigeria's help with diplomatic mediation between Zaire and Angola. Nigeria agreed but urged outside powers not to provide arms. Cuban President Fidel Castro denied that Cuba was involved in the conflict and called Mobutu "desperate" and the accusation being "a pretext to get military assistance from imperialism so he can continue to oppress the people of Zaire". Zaire had already been overdue on its loan payments, and the conflict increased the uncertainty of international banks of its ability to repay. A group of 98 banks, led by Citibank, had agreed in November 1976 to offer Zaire a $250 million loan if the country promised to implement economic austerity. The banks hoped that the additional loan would help Zaire develop its economy and pay back the $400 million that it already owned. The banks feared that the war would now bankrupt Zaire's government. Citibank announced on behalf of the group that the loan would be suspended until Zaire could resolve its internal problems, which would have jeopardised repayment. The FNLC progressed into Katanga. In a battle in Kasaji on March 18, the FAZ killed 15 of the FNLC soldiers and lost 4 of its own. On March 25, the FAZ abandoned Mutshatsha, and the FNLC entered it. The town had railway access and was 130 km from the Kolwezi, home to the Musonoi Mine, a major source of copper for Gécamines. The capture of Mutshatsha led observers to perceive a serious threat from the invading force. (Despite its economic importance, Kolwezi was not particularly well-defended. A Belgian manager suggested: "No one would dare to touch us. We are essential to whoever governs this area, so we are not worried.") Americans in Kolwezi, mostly workers for Morrison-Knudsen, were evacuated. The perception of the rebels' power increased as reports suggested they were beginning to provide social assistance to local people in the Shaba province. The FNLC began to establish a regional administration and to distribute identity cards for a nation called "The Democratic Republic of the Congo".