Sen. Bob Menendez (D-N.J.) on Monday urged President Trump to commit additional military assistance to Ukraine in response to Russian aggression near Crimea.

Menendez, the top Democrat on the Senate Foreign Relations Committee, called on the Trump administration to bulk up its security assistance to Ukraine, and suggested NATO increase exercises and its presence in the Black Sea.

The senator said Trump should commit additional resources to Ukraine prior to his expected meeting with Russian President Vladimir Putin at this weekend’s Group of 20 summit in Argentina.

{mosads}”Once again, the Kremlin has shown that it only respects a strong adversary that is willing to stand up to bullies,” Menendez said in a statement. “At this precarious time, the U.S. cannot afford a weak performance by President Trump at the G20, like we saw in Helsinki.”

“Mr. President, this is your opportunity to finally show American leadership in defense of our principles and our close allies across Europe,” Menendez added.

The Democrat also said Congress should pass the Defending American Security from Kremlin Aggression Act, which reaffirms support for NATO and carries additional sanctions against Russia.

The Kremlin only respects a strong adversary that is willing to stand up to bullies. At this precarious time, the U.S. cannot afford a weak performance by President Trump at the G20. He must show American leadership in defense of our principles and our close allies across Europe pic.twitter.com/wi5B66z331

— Senator Bob Menendez (@SenatorMenendez) November 26, 2018

The Ukrainian Navy said on Sunday that Russia fired on some of its ships in the Kerch Strait near Crimea, hitting two vessels and injuring two crew members. Russia then seized both ships and a tugboat, Ukraine said.

Russia annexed Crimea from Ukraine in 2014, prompting significant international backlash and sanctions against Moscow. The international community has not formally recognized the seizure of the territory.

Trump has drawn criticism at times for his reluctance to condemn Russia over its seizure of Crimea, among other topics. He has not publicly commented on Sunday’s clash.

U.S. Ambassador to the United Nations Nikki Haley said at a Security Council meeting on Monday that the Trump administration supports Ukraine, and called Russia’s aggression “an arrogant act that the international community must condemn and will never accept.”