The top US diplomat for European affairs, Wess Mitchell, has resigned.
The news come at a time of tension between the European Union and the Trump administration due to US tariffs on European steel and aluminium, the US pulling out of the Iran Deal and Paris agreement, and the recent decision to withdraw troops from Syria.
Mitchell was brought on by former Secretary of State Rex Tillerson in 2017 when US President Donald Trump threatened to withdraw the US from NATO.
In a letter tweeted by a CNN reporter on Tuesday to US Secretary of State Mike Pompeo, Wess said he felt he had completed his time at the post and wanted to spend more time with his young family.
Pompeo said on Twitter that Mitchell had done "an outstanding job as Assistant Secretary."
In his letter, Wess said he was "proud of diplomatic efforts in sustaining transatlantic unity on sanctions against Russia" as well as the work done to support a resolution in the Greece-Macedonia name dispute and increasing diplomatic engagement in Central Europe, the eastern Mediterranean and Western Balkans among other things.
Wess is set to leave his post on February 15, according to the State Department.