The current Army Secretary will take up his new position of Acting Secretary of Defense on Monday, June 24, before traveling to Belgium for the meeting on June 26 and 27.

The change comes after Patrick Shanahan, the role's present incumbent, withdrew his name on Tuesday from consideration for senate-confirmation, citing family concerns.

Esper's focus in Brussels will be on "reinforcing the US commitment to strengthening the NATO Alliance, ensuring more equitable burden sharing, bolstering NATO readiness and addressing regional security issues," Pentagon spokesperson Jonathan Hoffman said in a statement.

The third person to hold the position in just six months, Esper's arrival risks ruffling the feathers of European partners already disconcerted by President Donald Trump's isolationist policies and his propensity to monetize alliances.

Former Marine general Jim Mattis, who many US allies considered a guardian of international stability, departed the post last December.