U.S. Senator Rand Paul Thursday blocked a vote on a $40 billion aid package for Ukraine, slowing U.S. efforts to quickly deliver more help to Ukraine as it battles a Russian invasion.

“We cannot save Ukraine by dooming the U.S. economy,” Paul said.

A unanimous Senate vote would have expedited the delivery of aid to Ukraine.

Paul’s move, however, has delayed the vote for another week, when the Senate is expected to pass the bill.

Ukraine says negotiations are underway for the release of 38 incapacitated soldiers from the Azovstal steel plant in Mariupol in exchange for Russian prisoners.

In a post on Facebook, Deputy Prime Minister Iryna Vereschuk described the talks as “very difficult.”

She said comments by “some politicians, journalists and public figures,” about the talks have hurt the negotiation process and requested that people refrain “from making public comments on what you don’t know.” Finland’s President Sauli Niinisto and Prime Minister Sanna Marin Thursday expressed their approval for joining NATO, a move that would complete a major policy shift for the country in response to Russia’s invasion of Ukraine.

“NATO membership would strengthen Finland’s security. As a member of NATO, Finland would strengthen the entire defense alliance,” they said in a joint statement. “Finland must apply for NATO membership without delay. We hope that the national steps still needed to make this decision will be taken rapidly within the next few days.”

The leaders said they came to their decision after allowing time for Finland’s parliament and the public to consider the matter, and to consult with NATO and neighboring Sweden. Officials in Sweden are expected to consider their own possible NATO application in the coming days.

NATO Secretary General Jens Stoltenberg said Thursday if Finland does apply for membership, “they would be warmly welcomed into NATO and the accession process would be smooth and swift.”

“Finland is one of NATO’s closest partners, a mature democracy, a member of the European Union, and an important contributor to Euro-Atlantic security,” Stoltenberg said.

Russia has warned against NATO expansion, and said Finland and Sweden joining would bring “serious military and political consequences.”

“The expansion of NATO and the approach of the alliance to our borders does not make the world and our continent more stable and secure,” Kremlin spokesman Dmitry Peskov told reporters Thursday.

Ukrainian President Volodymyr Zelenskyy tweeted that he praised Finland’s decision in a phone call with Niinisto.

The fight for Ukraine played out beyond the battlefields Wednesday, with Kyiv shutting one Russian natural gas pipeline that supplies European homes and industry, while a Moscow-installed official in southern Ukraine said the Kremlin should annex the city of Kherson after Russian troops took control.

Ukraine’s natural gas pipeline operator said it was stopping Russian shipments through a hub in eastern Ukraine controlled by Moscow-backed separatists because of interference from enemy forces, including the apparent siphoning of gas.

About one-third of Russian gas headed to Western Europe passes through Ukraine, although one analyst said the immediate effect might be limited, since much of it can be redirected through another pipeline. Russia’s giant state-owned Gazprom said gas flowing to Europe through Ukraine was down 25% from the day before.

The European Union, as part of its announced effort to punish Russia for its 11-week invasion of Ukraine, is looking to end its considerable reliance on Russian energy to heat homes and fuel industries.

It has, however, encountered some opposition from within its 27-member bloc, especially from Hungary, which says its economy would sustain a major hit if its supply of Russian energy were cut off.

Meanwhile, Kirill Stremousov, deputy head of the Kherson regional administration installed by Moscow, told Russia’s RIA Novosti news agency, “The city of Kherson is Russia.”

He asked that Putin declare Kherson a “proper region” of Russia, much as Moscow did in 2014 in seizing Ukraine’s Crimea Peninsula and declaring Luhansk and Donetsk as independent entities shortly before invading Ukraine on February 24.

Peskov said that it would be “up to the residents of the Kherson region” to make such a request, and to make sure there is an “absolutely clear” legal basis for the action.

Ukrainian presidential adviser Mykhailo Podolyak derided the notion of its annexation, tweeting: “The invaders may ask to join even Mars or Jupiter. The Ukrainian army will liberate Kherson, no matter what games with words they play.”

Kherson is a Black Sea port with a population of about 300,000 and provides access to fresh water for neighboring Crimea. Russian forces captured it early in the war.

Some information for this story came from The Associated Press, Agence France-Press and Reuters.