There isn't an OOTB web service to do this, and it's by design. Web
Services are not well suited for transferring large files, which is why
one or more of FP-RPC, WSS-RPC, WebDAV, and HTTP PUT/POST are used
instead for the various MOSS/WSS clients. I'd suggest you look at using
one of those methods instead (FP-RPC and WebDav are usually best), as
they are all HTTP based and will be faster/better/more reliable than a
Web Service.