Washington — Lt. Gen. H.R. McMaster, a former national security adviser to Donald Trump, said Sunday that the upcoming months will be “really critical” in determining the “next phase” of the war in Ukraine as the president-elect is expected to work to force a negotiated settlement when he enters office.

McMaster, a CBS News contributor, said on “Face the Nation with Margaret Brennan” that Russia and Ukraine are both incentivized to make “as many gains on the battlefield as they can before the new Trump administration comes in” as the two countries seek leverage in negotiations.

With an eye toward strengthening Ukraine’s standing before President-elect Donald Trump returns to office in the new year, the Biden administration agreed in recent days to provide anti-personnel land mines for use, while lifting restrictions on Ukraine’s use of U.S.-made longer range missiles to strike within Russian territory. The moves come as Ukraine marked more than 1,000 days since Russia’s invasion in February 2022. 

Meanwhile, many of Trump’s key selection for top posts in his administration — Rep. Mike Waltz for national security adviser and Sens. Marco Rubio for secretary of state and JD Vance for Vice President — haven’t been supportive of providing continued assistance to Ukraine, or have advocated for a negotiated end to the war.

McMaster said the dynamic is “a real problem” and delivers a “psychological blow to the Ukrainians.”

“Ukrainians are struggling to generate the manpower that they need and to sustain their defensive efforts, and it’s important that they get the weapons they need and the training that they need, but also they have to have the confidence that they can prevail,” he said. “And any sort of messages that we might reduce our aid are quite damaging to them from a moral perspective.”

McMaster said he’s hopeful that Trump’s picks, and the president-elect himself, will “begin to see the quite obvious connections between the war in Ukraine and this axis of aggressors that are doing everything they can to tear down the existing international order.” He cited the North Korean soldiers fighting on European soil in the first major war in Europe since World War II, the efforts China is taking to “sustain Russia’s war-making machine,” and the drones and missiles Iran has provided as part of the broader picture.

“So I think what’s happened is so many people have taken such a myopic view of Ukraine, and they’ve misunderstood Putin’s intentions and how consequential the war is to our interests across the world,” McMaster said. 

On Trump’s selections for top national security and defense posts, McMaster stressed the importance of the Senate’s advice and consent role in making sure “the best people are in those positions.”

McMaster outlined that based on his experience, Trump listens to advice and learns from those around him. And he argued that the nominees for director of national intelligence and defense secretary should be asked key questions like how they will “reconcile peace through strength,” and what they think “motivates, drives and constrains” Russian President Vladimir Putin.

Trump has tapped former Rep. Tulsi Gabbard to be director of national intelligence, who has been criticized for her views on Russia and other U.S. adversaries. McMaster said Sunday that Gabbard has a “fundamental misunderstanding” about what motivates Putin.

More broadly, McMaster said he “can’t understand” the Republicans who “tend to parrot Vladimir Putin’s talking points,” saying “they’ve got to disabuse themselves of this strange affection for Vladimir Putin.” 

Meanwhile, when asked about Trump’s recent selection of Sebastian Gorka as senior director for counterterrorism and deputy assistant to the president, McMaster said he doesn’t think Gorka is a good person to advise the president-elect on national security. But he noted that “the president, others who are working with him, will probably determine that pretty quickly.”