Washington, April 29 : King Charles III warned that the world is entering a more volatile and dangerous phase, urging the United States and the United Kingdom to adapt their alliance to meet shifting global challenges.

Addressing a joint meeting of Congress, the British monarch said the international system is under strain from multiple crises.

â??We meet in times of great uncertaintyâ?¦ in times of conflict from Europe to the Middle East, which pose immense challenges for the international community,â?? he said.

He added that the world today is â??in many ways more volatile and more dangerousâ?? than previous decades, underscoring the need for renewed cooperation among allies.

Framing his remarks around a changing global order, Charles said longstanding alliances cannot rely solely on past achievements.

â??Our alliance cannot rest on past achievements or assume that foundational principles simply endure,â?? he said, calling for efforts â??to build on it.â??

The King described the United States-United Kingdom partnership as an â??indispensable partnership,â?? rooted in shared democratic traditions but now facing new pressures from geopolitical instability and security threats.

He said the challenges confronting the international system are too complex for any single country to handle alone.

â??The challenges we face are too great for any one nation to bear alone,â?? he said, urging closer coordination with international partners.

Charles pointed to security as the starting point for adapting to the new era, announcing that Britain is committing to â??the biggest sustained increase in defence spending since the Cold War.â??

He stressed that military and intelligence ties between the United States and Britain remain deeply integrated.

â??Our defence, intelligence and security ties are hardwired together through relationships measured not in years, but in decades,â?? he said.

The monarch also highlighted the importance of collective defence alliances, particularly NATO, describing it as central to protecting shared interests in a shifting security landscape.

Continued support for Ukraine is necessary â??in order to secure a truly just and lasting peace,â?? the King said and described the conflict as a test of Western resolve in the current global environment.

Beyond security, Charles identified economic and technological cooperation as critical pillars of the evolving global order.

He cited $430 billion in annual trade and $1.7 trillion in mutual investment between the two countries, and pointed to joint work in artificial intelligence, quantum computing and nuclear fusion as key to future growth.

â??Our nations are combining talent and resources in the technologies of tomorrow,â?? he said.

He also warned that environmental pressures are reshaping global stability, saying the â??collapse of critical natural systemsâ?? poses risks not only to nature but also to economic and national security.

In his closing remarks, Charles cautioned against inward-looking policies at a time of global transition.

He urged both nations to â??ignore the clarion calls to become ever more inward lookingâ?? and instead reaffirm their role in supporting international cooperation.

The address comes as the United States marks 250 years since its Declaration of Independence, a moment Charles described as an opportunity to renew commitments in a changing world.

/IANS