The top US military officer told lawmakers Tuesday that Russia’s invasion of Ukraine likely could not have been prevented except by the presence of US forces and warned that the conflict in Europe is likely to drag on for years to come.

Gen. Mark Milley, chairman of the Joint Chiefs of Staff, said the conquest of Ukraine had been a “long-standing objective” of Russian President Vladimir Putin.

The top U.S. military officer is warning that the war in Ukraine will likely last years, raising concerns that the world "is becoming more unstable and the potential for significant international conflict between great powers is increasing, not decreasing."

During testimony in front of the House Armed Services Committee on Tuesday, Chairman of the Joint Chiefs of Staff General Mark Milley called Russia's invasion of Ukraine "the greatest threat to peace and security of Europe, and perhaps the world, in (his) 42 years of service in uniform."

The highest ranking military officer in the U.S. said Tuesday that he expects the conflict in Ukraine to last years. 

"I do think this is a very protracted conflict, and I think it's measured in years. I don't know about decade, but at least years for sure," Chairman of the Joint Chiefs of Staff General Mark Milley told the House Armed Services Committee Tuesday during testimony on the defense budget.