Russia may be 'looking to move further' into Ukraine, its foreign minister warns

As it again masses troops and equipment on the border with Ukraine, the Russian government is "looking for the opportunity to move further" into Ukrainian territory, the country's foreign minister warned in an exclusive interview.

"We do not want to scare anyone, but we have to remain vigilant," Foreign Affairs Minister Dmytro Kuleba told ABC News. "We are extremely worried, but listen -- when you live next to Russia for seven years in an armed conflict, you kind of learn to be worried. You get used to it."

Kuleba just wrapped up a high-profile visit to Washington, meeting Wednesday with President Joe Biden's top foreign policy aides, Secretary of State Antony Blinken and National Security Advisor Jake Sullivan.

The visit was just the latest exchange between Biden's administration and that of Ukrainian President Volodymyr Zelenskiy, who was infamously urged by former President Donald Trump to announce an investigation into Biden and his son Hunter.

Kuleba noted the "turbulence" in U.S.-Ukrainian relations during the Trump years, but eagerly looked to turn the page -- saying ties were "revived, restored, relaunched, whatever word we use."

U.S. officials have tried to demonstrate that, too, expressing growing concern about Russia's military movements in recent weeks. Blinken said the U.S. commitment to Ukraine remains "ironclad" and warned Moscow that "any escalatory or aggressive actions would be of great concern by the United States."

As many as 100,000 Russian troops have been moved to its western border with Ukraine, Zelenskiy said Thursday. Satellite images published by the firm Maxar Technologies last week showed large ground forces deployed 140 miles from the border with heavy equipment, while the defense firm Janes said the buildup was largely covert, with elite ground units and often taking place at night, according to Bloomberg News.

Russian government officials denied the movements, then dismissed concerns about them and accused the U.S. and NATO of aggression.

Ukrainian officials have swung between raising alarm at Russia's recent actions and downplaying them as a tactic by Russian leader Vladimir Putin meant to create hysteria.

"Russia's psychological pressure has not worked on us for a long time. Your panic will definitely not help, but it can help the enemy. It can become part of the information war and bring no less harm to the country than the fighting," Zelenskiy said Thursday.

Standing alongside Kuleba on Wednesday, Blinken said, "We don't have clarity into Moscow's intentions, but we do know its playbook," recalling Putin's 2014 invasion of Ukraine's territory, Crimea, which it still occupies, and incursion into eastern Ukraine. That still-smoldering war between Russian-backed separatists and the Ukrainian government has claimed 14,000 lives and counting.

That playbook can be swiftly executed, Kuleba warned, because a similar military buildup in April ended with troops departing, but the infrastructure and equipment largely remaining in place.

"With this infrastructure in place along our border, it will not take Russia a lot of time to resort to an offensive action if it decides to do so, and our goal and our objective is to make everything, everything possible to prevent Russia from making that decision," he told ABC News.

Part of that effort is boosting U.S. military assistance to Ukraine, which both Kuleba and Blinken called for after their meetings Wednesday. Blinken declined to offer specifics, but Kuleba called for greater intelligence sharing, air defense systems and more.

The Biden administration has been "very specific and very committed" in responding to Russian aggression, he told ABC News, taking a "proactive stance" and walking the walk.

"What is even more important from my conversations here in Washington, I see that the United States are ready not only to talk, but also to act, to act in order to deter Russia and to strengthen Ukraine's capacity to defend itself," he said. "This is even more important."

Selling Ukrainian lethal weapons was at the heart of Trump's first impeachment and the infamous call between him and Zelenskiy. As the newly elected Ukrainian leader asked Trump for more Javelin anti-tank missiles, Trump turned the conversation to ask for a "favor" and announce a probe of Biden, his son Hunter and Hunter's time on the board of the Ukrainian state-owned energy company Burisma.

While there was no announcement about new weapons sales, Kuleba said he was "leaving Washington, D.C., in a good mood because this is exactly what we were working for."

"The truth is, there has been some turbulence in our bilateral relations under the previous administration. There was some hesitations of how this relationship will proceed further in the early days of this administration. But I think that it will not be an exaggeration to say that the quality and the number of contacts between our presidents, between me and foreign secretary, and at all other levels of our teams has been unprecedented," he told ABC News.

But that's not to say there aren't critical differences now, even on the potential threat from Russia. During their joint press conference Wednesday, Blinken refused to say Russia is using energy as a weapon, while Kuleba clearly said it already is, including by halting coal shipments to Ukraine and withholding greater natural gas imports through Ukraine to Europe amid an energy crisis across the continent.

"What is unfolding in Europe now is a very complicated game with many elements in it," Kuleba said at the State Department, accusing Russia and its ally Belarus of pressuring Europe using energy, propaganda and disinformation, cyber attacks, military buildups, and the migration crisis between Belarus and its neighbors.

Biden has called for stabilizing U.S. relations with Russia, including by holding his summit with Putin in June -- a meeting that could have a sequel soon. Kuleba said he understands the sentiment and sees no "risks" that U.S.-Russian dialogue would be "done at the expense of Ukraine," but he warned that Putin only responds to strength.

"Our experience of recent seven years demonstrates that Moscow understands and respects the language of strength. You do not have to threaten them, you do not have to act, to use force against them, but they respect you if you are strong with them, if you are tough with them," he said.

One issue, however, where critics say the U.S. is not standing strong is Nord Stream 2, the nearly completed natural gas pipeline connecting Russia and Germany and circumventing Ukraine, Poland and other U.S. partners. Biden waived congressionally-mandated sanctions on the German company constructing the pipeline and its CEO, saying he did not want to damage ties with a key ally. Instead, the U.S. and Germany issued a joint statement, committing to helping Ukraine diversify its energy resources and responding swiftly if Russia withholds gas to Ukraine.

But joined by Poland, Kyiv expressed anger and dismay at the non-binding agreement. Kuleba papered over that disagreement, saying what was most important is that they were talking -- but urged action if needed.

"We have differences in seeing how the negative consequences of this project being implemented can be avoided or prevented," Kuleba told ABC News. "We definitely want the United States to remain vigilant and ready, ready to take action if the current policy fails."

ABC News's Yulia Drozd contributed to this report from Kyiv.