The Metro system in the United States capital is in such bad need of repairs that officials warned they may have to shut down entire rail lines for as long as six months in order to complete work.

Such a closure would complicate hundreds of thousands of commutes and increase traffic in a region already jammed daily.

Metro officials disclosed this possibility to other Washington DC leaders at a recent conference and it is becoming increasingly likely that a long-term Metro shutdown is in the cards, according to the Washington Post.

"The system right now, in order to do the maintenance that needs to be done, cannot be done on three hours a night and on weekends. It just can't," Metro Board Chairman Jack Evans, who is also a DC councilman, said to the Post. "So in order to do repairs that are necessary, it may come to the point where we have to close the entire Blue Line for six months.

"People will go crazy. But there are going to hard decisions that have to be made in order to get this fixed."

DC's Metro averages just over 700,000 riders per weekday, according to the system's website, making it the third most-used subway line in the US, behind New York and Chicago. The system has six train lines.

Metro General Manager Paul Wiedefeld, who took over the system in November, said no decisions have been made about closing entire lines for repair work. The Post reported that a decision is expected to be made within six weeks.

Mr Evans said that any of the Metro's six lines could be shuttered, at least in part. He said the city's Red Line was the one least likely to be shut.