LONDON, April 22 (Reuters) - U.S. assets and personnel overseas could be at risk if the country decided to pass a bill against OPEC, known as NOPEC, the head of the Organization of the Petroleum Exporting Countries told member states.

In a letter, seen by Reuters, Mohammad Barkindo encouraged member countries to engage with the U.S. administration.

"It is essential that member countries reinforce diplomatic bilateral contacts with government officials in the U.S. ... and explain the disadvantages for the U.S. should the NOPEC bill become law".

"These disadvantages might include: weakening the immunity principle at a global level, putting at risk U.S. interests overseas, and the protection for their personnel and assets," the letter said. (Reporting by OPEC Team, writing by Dmitry Zhdannikov, editing by Chris Reese)