Amid whisperings that the Justice Department will file criminal corruption charges against Sen. Robert Menendez, D-N.J., the long-time senator today spoke about the importance of the U.S. standing strong against Russia and warned that inaction could embolden countries with nuclear capabilities.

“The simple fact is we all want a diplomatic solution to this problem. But I believe this can only come about when Putin believes that the cost of continuing to ravage Ukraine is simply too high,” he said. “We have a responsibility to increase that cost.”

Menendez, speaking alongside former National Security Adviser Zbigniew Brzezinski, addressed a full house at the Center for Strategic and International Studies in Washington, D.C., on how the U.S. should respond to Russia’s aggression against Ukraine.

“It has never been in our nature to simply observe,” he said of the United States. “In my view, it is in our strategic interest to be an active participant in leading any effort to counter Russia.”

Menendez, the ranking member of the Senate Foreign Relations Committee, has been a leading voice in calling for additional sanctions against Russia and advocated for the U.S. to arm Ukrainians as the neighboring country continues to make territorial gains.

The U.S. has sent nonlethal military aid to Ukraine, including blankets and night vision goggles, but Menendez joined a chorus of Republican and Democratic lawmakers pushing for lethal aid.

“That’s all well and good if I can see the enemy, but I have no wherewithal to stop them. It really is not responding to the fundamental challenge,” he said.

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Specifically, the New Jersey senator called on the president to provide the country with equipment like counter-artillery radar, surveillance drones, anti-tank and anti-armor weapons, and ammunition.

Military leaders including Chairman of the Joint Chiefs of Staff Martin Dempsey and Secretary of Defense Ashton Carter back calls to arm Ukrainians. The president hasn’t yet said whether he will approve lethal aid to the country, but hasn’t ruled it out either.

“We need to send a very clear global message: If you violate and upend the international order, there will be consequences,” the New Jersey Democrat said. “And we have to mean it when we say it, and we have to back up our words with a menu of agreed upon actions that will follow. There should be no ambiguity about either our resolve or what actions we would consider.”

Menendez warned that the country’s response to Russia is being looked at by other global actors—particularly those with nuclear capabilities.

“Whether it’s China in the South China Sea that has territorial disputes with our allies, South Korea and Japan, or the challenge we face with a nuclear-armed North Korea, or the challenge of [President Nicolás] Maduro in Venezuela oppressing his people—I could go through a long list of global actors who, in the absence of assured consequence for violating the international order, will be emboldened,” he said. “That is an incredibly risky world to live in.”

The senator’s speech on Russia came just days after CNN reported that the Justice Department will file criminal corruption charges against the long-time senator. The charges center around his relationship with friend and political donor Salomon Melgen and are the culmination of a two-year investigation into the duo’s ties.

Menendez hasn’t been indicted yet, and the looming threat of the charges hasn’t stopped him from speaking out against the president’s policies.

“The United States must lead,” he said in closing today. “American leadership counts.”