Dozens of countries do not currently have a senate-confirmed US ambassador in place, including key US allies like South Korea, Jordan, and Saudi Arabia.
Of these vacant posts, over 30 are still awaiting a nominee, while 11 others have nominees pending confirmation.
Additionally, President Donald Trump has yet to nominate people for senior roles at many international organizations, and to oversee important regional and issue-based bureaus.
As his administration grapples with an increasingly aggressive North Korea, Trump lacks not only a permanent ambassador to South Korea, but also a permanent Undersecretary for Arms Control and International Security Affairs, and a permanent Assistant Secretary for East Asian and Pacific Affairs.
And with conflicts raging in Syria, Iraq, and Yemen, key positions in the Middle East also remain unfilled.
As of Wednesday, two of the agency's six undersecretary positions remained open, along with most of the assistant secretary roles.
While senior acting official hold the reins in these important jobs, they are not permanent appointees, and are limited in how long they can hold these roles.
Federal law allows these temporary office-holders to stay in these open jobs for, at most, 300 days. But 320 days have elapsed since the start of the Trump administration and acting officials in the State Department are starting to hit that limit, making presidential nominations more important than ever.
In his public remarks, Tillerson has acknowledged the persistent vacancies, while fiercely defending the acting officials who have stepped up to the plate.
Some of the blame, he insists, lies with the senate, who are responsible for confirming the President's nominees.
But a recent CNN analysis shows that it has taken an average of approximately 65 days for the senate to confirm Trump's State Department nominees so far -- nearly identical to the 63-day average former President Barack Obama experienced during his first year in office.
The longest-pending ambassadorial nominee is K.T. McFarland, Trump's pick as ambassador to Singapore, who is facing a hold on her nomination until she addresses questions about her knowledge of communications between former national security adviser Michael Flynn and Russian ambassador Sergey Kislyak.
President Trump has been slower than his recent predecessors to nominate State Department personnel. He has made 75 nominations for the State Department and US Mission to the United Nations, compared to well over 100 by this date in the first year of Obama's and George W. Bush's administrations.
CORRECTION: The graphic in the story has been updated to reflect the fact 33 ambassador vacancies are awaiting nominees.