Sen. Rand Paul, R-Ky., single-handedly sidelined the $40 billion emergency Ukraine aid bill until next week in an effort to force lawmakers to include funding for a new watchdog effort to police how the billions in taxpayer dollars are spent.

In a very rare moment, Senate Majority Leader Chuck Schumer and Senate Minority Leader Mitch McConnell joined forces.

"There is now only one thing holding us back: the junior Senator from Kentucky is preventing swift passage of Ukraine aid because he wants to add -- at the last minute -- his own changes directly into the bill. His change is strongly opposed by many members from both parties," Schumer said Thursday. "He is not even asking for an amendment … he is simply saying, 'my way or the highway.'"

But Paul stood his ground, highlighting the nearly $60 billion that the U.S. will have given to Ukraine if this package passes.

After Paul blocked an effort to expedite passage, Schumer reiterated that Paul will not get his desired changes without a vote and blamed Paul for slowing aid.

The aid bill has enormous bipartisan support and is expected to pass by sometime next week.

-ABC News' Trish Turner and Allie Pecorin

The United States "would support" Finland and Sweden applying to join NATO "should they choose to apply," White House press secretary Jen Psaki said on Thursday.

"We, of course, will respect whatever decision they make. Both Finland and Sweden are close and value defensive partners of the United States and of NATO," she said.

If the countries do apply, Psaki said, it "should be reassuring to the American people about our own security interests."

"Having a strong NATO alliance, a strong Western alliance, that's a defensive alliance, by the way, it is good for our security around the world, certainly having a strong partnership with a range of countries, including Sweden and Finland," she said.

-ABC News' Justin Ryan Gomez

Russian Deputy Ambassador to the United Nations Dmitry Polyanskiy told a British news podcast that Finland and Sweden officials "know the moment they become members of the NATO, it will imply certain mirror moves on the Russian side."

"If there are NATO detachments in those territories, these territories would become a target -- or a possible target -- for a strike," Polyanskiy warned.

He continued, "NATO is a very unfriendly bloc to us. … It means that Finland and Sweden all of a sudden, instead of neutral countries, become part of the enemy and they bear all the risks."

Despite repeated claims by Russian President Vladimir Putin that NATO’s expansion is a risk to Russian security, Polyanskiy insisted the addition of Finland and Sweden to the alliance would have little impact.

"I don’t think it will really be a blow to the security of Russia because these two states become members of NATO -- hopefully they won’t, but if they do it would be the worst solution for them, but not for Russia," he said. "Russia is ready to face NATO threats. Russia has made the necessary precautions for this."

The Russian Foreign Ministry said earlier that Russia "will be forced to take retaliatory steps both of military-technical and of other nature in order to stop the threats to its national security" should Finland become a NATO member.

While Britain has pledged military support for both Sweden and Finland if they were to come under attack, regardless of whether the countries are accepted into the alliance and under the umbrella of NATO's Article 5, the U.S. has yet to make a similar bridge security guarantee.

Testifying before the Senate Foreign Relations Committee on Thursday, Assistant Secretary of State for European and Eurasian Affairs Karen Donfried said, "We will surely find ways to assure Finland and Sweden, but the nature of that is still to be worked out."

-ABC News' Shannon Crawford

About 12 Russian missiles struck in and around the Kremenchuk oil refinery in central Ukraine, according to Dmytro Lunin, head of the Poltava Regional Military Administration.

No one was injured and crews have extinguished the blaze, Lunin said.

Most missiles hit the infrastructure of the refinery, which is not operating, Lunin said.

-ABC News' Irene Hnatiuk and Yuriy Zaliznyak

White House national security advisor Jake Sullivan hinted Thursday of more sanctions coming against Russia in the "next week or two" aimed at targeting ways Moscow is evading sanctions already imposed.

“Where our focus will be over the course of the coming days is on evasion,” Sullivan said Thursday at the Economic Club of Washington. “As Russia tries to adjust to the fact that it’s under this massive economic pressure, what steps do they take to try to evade our sanctions and how do we crack down on that? And I think we'll have some announcements in the next week or two that identify targets that are trying to facilitate that evasion both inside Russia and beyond."

When Sullivan was asked whether sanctions will automatically be lifted if a negotiated peace deal between Russia and Ukraine is worked out, he appeared cautious with his words, saying, “a lot of that depends on what the shape and scope” of the agreement is.

“A lot of it depends on what the Ukrainians, in consultation with us and the Europeans come to agree to," Sullivan said. "You know, we're not going to do a deal over the head of the Ukrainians where we give a bunch of sanctions relief to Russia. But if some measure of sanctions relief were built in to some credible diplomatic solution led by the Ukrainians, that's something that we would happily discuss."

But Sullivan said Russian oligarchs shouldn't expect to ever get back their yachts and other assets seized under sanctions that have been imposed, saying the ultimate goal is "not to give them back” once the war is over.

“The president is actively looking at how we can deal with the fact that as we seize these assets, our goal is not to give them back. Our goal is to put them to a better use than that," Sullivan said. "But I'll be careful in what I say today because there's an ongoing kind of policy process around how we end up dealing with that question. But, rest assured, that the goal is not just to sit on them for a while."

-ABC News' Justin Gomez