The leaders of NATO countries have kicked off their two-day summit in Lithuania. Support for Kyiv is expected to top the agenda.

NATO Secretary General Jens Stoltenberg said: "Today we will make many decisions for an even stronger alliance. We will increase our practical and political support for Ukraine. This will bring Ukraine closer to NATO where it belongs. We will also take both steps to further strengthen our deterrence and defense, including new plans and forces for the defense of the Euro-Atlantic Area."

Leaders of NATO'S 31 member states are meeting in Vilnius, just a few hundred kilometers north of Ukraine. Japanese Prime Minister Kishida Fumio will take part in the talks after visiting Poland.

Swedish Prime Minister Ulf Kristersson is also attending. His country is now set to become NATO's 32nd member, after gaining support from Turkey.

But President Volodymyr Zelenskyy says he's disappointed his country isn't being welcomed as its 33rd. The Ukrainian leader is scheduled to take part in the talks.

Ahead of the summit, he vented frustration on twitter. Zelenskyy called delays in welcoming Ukraine into the alliance "unprecedented and absurd." He says it's motivating Russia to "continue its terror."

Speaking earlier, Zelenskyy said Ukraine was already a key part of NATO.

He said: "Ukraine is de facto already in the alliance. Our weapons are the weapons of the alliance. Our values are what the alliance believes in."

NATO began considering Ukraine's membership in 2008, but the country has struggled to meet some requirements. The country also can't join while its war with Russia is ongoing, because doing so would risk bringing nuclear-armed states into direct conflict. But debate is ongoing over how quickly Ukraine will be allowed into the alliance once the war ends.

Meanwhile, Ukraine's counteroffensive appears to be going slower than expected. Zelenskyy is still expected to appeal for more weapons and training from NATO to speed up its fight to retake land taken by Moscow.