Wireshark-users: [Wireshark-users] Convert from NA Sniffer (Windows) 2.00x to libpcap

I have some traffic that is of NA Sniffer (Windows) 2.00x type that I wish to convert to libpcap, so I can run it through TCP replay. I've been trying to use editcap:

editcap -F libpcap input.cap output.pcap

But I keep getting the error "Can't open or create output.pcap: Files from that network type can't be saved in that format". 

Is there another way to convert the file?

Thank you.