"We don't think that ad hoc international tribunal would be effective", Sales told reporters. "They cost a fortune… and don't have the same track record of delivering justice that national-level courts do".
Sale pointed out that the fate of Daesh terrorists, who are now held in custody in various Middle Eastern countries, was a major issue on the agenda of the Global Coalition to Defeat Daesh Small Group, which convened on Thursday in Washington.
Sales reiterated the United States' support for the repatriation of Daesh terrorists to their native countries.
"Our view is that it is not a feasible option, it is not a viable option to ask other countries in the region to import other countries' foreign fighters and pursue persecution and incarceration there", Sales said.
US Special Representative for Syria Engagement James Jeffrey, who participated with Sales at the press briefing, said differences of opinion on the issue remain among senior officials from about 35 countries and organisations who attended the Small Group's meeting in Washington.
Earlier, US Secretary of State Mike Pompeo said that the member-states should take back terrorists detained in Iraq and Syria, and make them accountable.
*Daesh (also known as ISIS/ISIL/IS) is a terrorist group outlawed in Russia