From the U.S. Embassy in Moscow:
The U.S. Embassy Moscow's Consular Section reminds applicants that additional administrative processing is often required for individuals involved in scientific or technical fields of work or study. The possibility that your visa may be subject to additional processing is not regarded as an emergency for the purpose of granting expedited business appointments.
From the U.S. Embassy in China:
The U.S. Embassies in China recommend that business travelers and tourists make their appointment early and interview as far in advance of their planned travel as possible. Applying several months in advance will ensure that the embassy has the necessary time to conduct the interview, review the application, and determine whether a visa can be issued. The majority of visas can be processed in several days; however, some visa applications require additional administrative processing. Administrative processing for business and tourist visas is currently taking about 16 weeks.
The average visa processing wait time is the number of working days after a consular officer decides to issue a visa, for the passport and visa to be returned to the applicant. The majority of visas in Beijing are processed and returned to the applicant within several days.
Average visa processing wait time DOES NOT include the time required for administrative processing. These procedures require additional time. When administrative processing is required, the timing will vary based on individual circumstances of each case. Visa processing wait times can change.
Administrative processing for student and exchange visitor visas is currently taking approximately six to eight weeks.
Administrative processing for other classes of visas is currently taking approximately 14-16 weeks.