The inspector general of the Pentagon announced an inquiry into the recent medical treatment of US Defense Secretary Lloyd Austin and his failure to notify the broader government of his hospitalization was launched, according to a memo released on Thursday.

For more than a month, Austin did not disclose his prostate cancer diagnosis to President Joe Biden and Congress, and he refrained from informing them about his hospitalization at the start of the year for several days. This has resulted in increasing demands for his resignation or termination.

This situation poses a significant challenge for Biden in an election year, forcing the president onto the defensive and creating an opportunity for Republicans to criticize him as being too old for the job.

"The objective of the review is to examine the roles, processes, procedures, responsibilities, and actions related to the Secretary of Defense's hospitalization in December 2023 - January 2024," the memo said, referring to Austin's hospitalizations for prostate cancer treatment and subsequent complications.

The probe will also assess whether Defense Department "policies and procedures are sufficient to ensure timely and appropriate notifications and the effective transition of authorities as may be warranted due to health-based or other unavailability of senior leadership," it added.

Read more: US defense chief's hospitalization kept secret amid Middle East crisis

70-year-old Austin underwent a minor surgery to address the cancer on December 22. However, he faced complications, such as nausea and severe pain, leading to his readmission on January 1.

The White House was not made aware of Austin's hospitalization until last Thursday, with Congress being informed on Friday. President Biden only learned of the cancer diagnosis this week.

In reaction, White House Chief of Staff Jeff Zients, along with Austin's Chief of Staff Kelly Magsamen, initiated an urgent review of the protocols for handling the incapacitation of senior US officials.

The undisclosed hospitalization of the secretary left a crucial national security official unaccounted for during a period when Washington's forces face frequent operations on the part of resistance groups in Iraq and Syria, while the Yemeni movement Ansar Allah is targeting Israeli-linked shipping in the Red Sea.

Read more: US Defense Secretary Austin recovering following cancer surgery