PARIS (Reuters) - Dubai's Emirates, one of the world's largest cargo carriers, is expanding its fleet of Boeing 777F freighters as it plans for sharp growth in cargo traffic, industry sources said.

The order for more of the current-generation freighters emerged amid tensions between Emirates and Boeing ( BA ) over separate delays but pre-dated Boeing's ( BA ) announcement on Friday that its future 777X jetliner series would slip by another year to 2026.

In September, Boeing ( BA ) reported orders from unnamed buyers for 11 777F freighters, but did not supply details. The sources said part of the total included a fresh order for the 777F from Emirates. The airline and Boeing ( BA ) both declined comment.