A collection of about 2,000 posters from the World War I era by US army officer Edward H. McCrahon will be sold at auction later this month, Guernsey's auction house said.

The collection, which is being sold by Mr McCrahon's heirs, will go under the hammer during an online, unreserved auction with no minimum bids on June 30 and July 1.

It includes the famous poster of a stern-looking, top-hatted Uncle Sam pointing a finger with the words "I want you for US army".

Enlist in the Navy. ( invaluable.com )

Another patriotic poster shows the American flag and labourers with the words "Teamwork wins", while a third is of French women working in a laundry and is inscribed "Four years in the fight".

"It's the best [collection] in the world," Guernsey's president Arlan Ettinger said.

"It appears that from the very beginning it was always looked at as the most comprehensive assemblage of posters of many different nationalities pertaining to their involvement in WWI."

Although all of the posters — works of art which are expected to fetch between $200 to $5,000 a piece — are patriotic, their topics range from fundraising and food rationing to women's war efforts, enlistment and animal aid.

About half of the posters are from the US, while others are in various languages from more than 15 countries including France, Italy, Germany, Canada, Cuba and China.

Many are by prominent illustrators, including J.C. Leyendecker and Howard Chandler Christy, and are among the only known copies in existence.

"There are many posters in this collection that have never been seen before," Mr Ettinger said.

"It really is a time capsule of a different era, when these things were very stirring, patriotic and treasured."

Brooklyn-born Mr McCrahon started the collection after he joined the French army two years before the US entered the Great War in 1917.

He became enthralled with the colourful, graphic posters encouraging citizens to support the war, and continued collecting after enlisting with the US armed forces.

When WWI ended Mr McCrahon devoted all of his time to enlarging the collection, and by the 1930s he began to exhibit it around the country.

One of the Thousand Y.M.C.A. Girls in France. ( invaluable.com )

Reuters