The American Charge d'Affaires in Ankara, Philip Kosnett, said there is a "strong sense of unity in Congress between Republicans and Democrats" that Brunson - accused of belonging to a terrorist organisation which Turkey blames for a failed coup - should be released.
Kosnett added: "[There is] a similar sense of unity between Congress and the administration that in order for the relationship between Turkey and the US to progress, we need to resolve that status not only for Brunson but also for other American citizens and local Turkish employees of US missions who we feel are detained unjustly under the state of emergency."
Republican Lindsey Graham and Democrat Jeanne Shaheen, both Senators, visited Turkey's capital last week to meet President Recep Tayyip Erdogan to directly appeal for Brunson's release.
Speaking about what he hoped the trip would achieve, Shaheen told the New Hampshire Union Leader: "Pastor Brunson has been unjustly imprisoned and kept away from his family for well over one year. The opportunity to see him and his wife, Norine, and to appeal directly to President Erdogan, were my main objectives on this trip."
Brunson was summoned to a local police station in October 2016 and later charged with links to a failed plot to overthrow the Turkish government in July 2016. He has been told he faces up to 35 years in prison.
Supporters claim he is effectively a political prisoner being held as a bargaining chip by Turkey as it seeks the extradition of preacher Fethullah Gülen, which it blames for the failed coup.
The Turkish presidency has not responded to the statements.
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