U.S. Defense Secretary Lloyd Austin’s planned trip to Brussels for NATO meetings was abruptly canceled due to his admission to a critical care unit at Walter Reed Military Medical Center.

The Pentagon announced his hospitalization on Sunday for symptoms indicating a serious bladder issue, complicating previous health concerns from undisclosed prostate cancer surgery in December and its subsequent complications.

Austin’s absence casts a shadow over discussions on NATO defense strategies and support for Ukraine amidst Russia’s invasion. While he was set to attend meetings on Thursday, including a gathering of NATO defense ministers and discussions with allies regarding Ukraine’s defense needs, the Pentagon has shifted these to virtual formats.

Deputy Secretary of Defense Kathleen Hicks now assumes Austin’s responsibilities during his hospitalization. The timing is sensitive, given Austin’s upcoming testimony before Congress regarding the secrecy surrounding his initial hospitalization.

Concerns over Austin’s health have sparked political debate, with Republicans criticizing his lack of transparency, while President Joe Biden has expressed confidence in him despite the lapses in disclosure. Austin recently apologized for not informing Biden and senior staff about his cancer diagnosis earlier.

Meanwhile, the U.S. Senate moves closer to passing a significant $95.34 billion aid package, with a focus on supporting Ukraine, Israel, and Taiwan. The legislation, if approved, would allocate $61 billion to Ukraine, vital as the country faces ongoing challenges amidst Russia’s invasion.

Former President Donald Trump’s controversial remarks over the weekend, suggesting a reluctance to defend NATO allies not meeting defense spending targets, have drawn widespread condemnation. Trump’s comments add to the geopolitical tension surrounding defense and security alliances, raising concerns about future transatlantic relations.