U.S. Secretary of State Antony Blinken will return to Brussels this week for discussions on Iran, Afghanistan and Russian activities directed at Ukraine, a U.S. official said.

Blinken will join U.S. Defense Secretary Lloyd Austin in Brussels. The official, speaking on condition of anonymity on Saturday, did not release additional details on the trip.

Austin was scheduled to visit NATO headquarters in Belgium on a trip that started on Saturday and also includes Israel, Germany and Britain, the Pentagon said last week.

The trip by two of President Joe Biden’s Cabinet members coincides with increasing tensions over Russian activities near Ukraine’s eastern border, where Washington says Russia has amassed more troops than at any time since 2014, when it annexed Crimea.