BRUSSELS — Ukraine on Monday officially started European Union membership negotiations, launching a process that will require its government to commit to years of political reforms even as it fights a Russian invasion.

Ukrainian Deputy Prime Minister Taras Kachka took part in an intergovernmental conference in Luxembourg to open talks that will help Kyiv align with the 27-member bloc’s laws, standards and values.

“Aggression against Ukraine and threats against Europe is a permanent policy of Russia, so that’s why we need to be united,” Kachka told journalists. “That’s why we need faster and very comprehensive accession to the European Union.”

Ukraine sees EU membership as a security guarantee for a stable future once the war ends. Its best guarantee would be membership in the NATO military alliance, but the Trump administration insists that cannot happen, and others are wary of it joining while the war continues.

Moldova also officially launched its membership talks. Russia has long tried to keep the country within its orbit, and last year Moscow was accused of waging a disinformation campaign driven by artificial intelligence during elections.

Countries hoping to join the EU must complete negotiations in 35 policy areas, or chapters, from agriculture to taxation and energy to trade, a process which can take years.

Monday’s meeting saw the opening of five key chapters — grouped as “clusters” — that underpin the values and principles on which the bloc was founded, notably the rule of law, fundamental rights and the functioning of democratic institutions.

The chapters are judiciary and fundamental rights, justice, freedom and security, public procurement, and statistics and financial control. The cluster is important for some EU countries that worry about Ukraine’s ability and willingness to fight corruption.

Last month, two national agencies fighting corruption named Ukrainian President Volodymyr Zelenskyy’s former chief of staff as an official suspect in a major graft investigation, but they said the Ukrainian leader was not under suspicion.

Some European countries have pushed to get Ukraine in the bloc as quickly as possible. They see Ukraine as vital to Europe’s security and have helped bolster its armed forces.

Last month, German Chancellor Friedrich Merz urged his EU partners to consider offering Ukraine “associate membership” to help breathe new life into talks aimed at ending more than four years of war with Russia.

Other countries — France and the Netherlands among them — have suggested work-arounds to bring Ukraine into the fold more quickly but without the rights of full membership.

But EU officials, and other countries waiting in line to join the bloc, insist that it should be a merits-based process that leads to nothing less than full membership.

Finland’s Foreign Minister Elina Valtonen said that completing the full reform process is vital, and that membership is not simply about securing a “club card for the EU.”

What Ukrainians “truly are after is freedom, democracy and a transparent market economy without any corruption,” she told journalists in Luxembourg.

Ukraine’s accession process was long stymied by Hungary under stridently nationalist former Prime Minister Viktor Orbán, who was considered Russia’s strongest ally in Europe and a possible threat to the EU project. He lost an election this year.

Orbán routinely exploited voting rules that require all 27 member countries to agree on certain rules, sanctions and even political statements. Indeed, unanimous agreement is required for each negotiating chapter to be opened, and then again for it to be closed.

The European Commission froze billions of euros in funds for Hungary in response to democratic backsliding led by Orbán, and concern lingers about the damage that can be done when one unhappy government insists on wielding its veto.

“We need to be very cautious in the future and make sure that these are countries that really want to be a part of Europe, and a part of the European Union, and are willing to work with us,” Swedish Foreign Minister Maria Malmer Stenergard said.

“In order for the EU to be really strong, we need to make sure that this doesn’t happen again,” she said.