The National Institute of Standards and Technology (NIST) is backing Microsoft's effort to certify Office Open XML as an international standard.

The U.S. standards body said on Friday that it has voted to conditionally approve Office Open XML (OOXML) pending some technical concerns in an upcoming standards approval vote.

NIST is part of the committee that will establish the United States' position in a September 3 vote at the International Organization for Standardization (ISO). Microsoft is seeking ISO standardization as a way to appeal to government customers concerned over long-term archiving of digital documents.

OpenDocument, or ODF, is another standard document format already approved by ISO. Advocates of ODF argue that a single standard is preferable while Microsoft executives argue that multiple standards provide more customer choice.

"NIST believes that ODF and OOXML can co-exist as international standards," NIST director William Jeffrey, said in a statement. "NIST fully supports technology-neutral solutions and will support the standard once our technical concerns are addressed."

NIST is a member of the InterNational Committee for Information Technology Standards (INCITS) executive board, which will form the U.S. position in the upcoming ISO vote.