Ukrainian President Volodymyr Zelensky on Thursday warned that any "pauses" in Ukraine's defence against the Russian invasion would only help Moscow to re-arm and allow it to "run us over".
He was speaking from Estonia, as Moscow and Kyiv accused each other of targeting civilians with missile strikes in a sharp escalation of attacks.
Zelensky was visiting the Estonian capital Tallinn on the second stage of a tour of staunch Baltic allies, part of efforts to bolster support for Kyiv with the war nearing its second anniversary.
"Give the Russian Federation two to three years, then they will simply run us over," he said at a news conference with the Estonian President Alar Karis.
"We wouldn't take that risk... There will be no pauses in favour of Russia."
A "long war" with Russia would not be good for Ukraine, Zelensky insisted.
Karis called for "no limits on providing Ukraine with arms", also suggesting that Kyiv should be allowed to strike inside Russia with Western weapons.
"We must understand that in a war it's inevitable to attack the military objects of the aggressor, to slow the enemy's forces down and weaken them," he said.
Earlier in January, Polish Foreign Minister Radoslaw Sikorski called on Western allies to deliver long-range missiles to Ukraine to help Kyiv target Russian "launch sites and command centres".
In Tallinn, Zelensky restated Ukraine's credentials for NATO membership, arguing that its army would strengthen the bloc's eastern flank.
NATO would gain "an army with military experience -- not theory but practice", he said.
Ukraine has expressed some frustration towards Western allies for the lack of a timeframe to join the security alliance.
Zelensky also acknowledged that military-aged Ukrainian men had illegally left the country to evade army service.
"If they are of mobilisation age, then they should help Ukraine. And they should be in Ukraine," he told reporters in Estonia.
Local Ukrainian officials said two Russian missiles had hit a hotel in the city of Kharkiv late on Wednesday, injuring 13 people including foreign journalists.
"There were no military personnel there," Mayor Igor Terekhov posted on Telegram.
Hours earlier, the authorities in the Russian border city of Belgorod said on Wednesday they had evacuated dozens of children following deadly Ukrainian missile strikes there.
Zelensky arrived in Tallinn overnight along with Foreign Minister Dmytro Kuleba.
Estonia, one of Ukraine's main allies and a NATO member, has called for continued support for Kyiv as some allies waver.
"Freedom should be better armed than tyranny," Estonian premier Kaja Kallas told reporters speaking alongside Zelensky in Tallinn.
She also reiterated her government's pledge to spend 0.25 percent of the country's Gross Domestic Product (GDP) on military aid to Ukraine over the next four years.
"We hope that this will be an example to everyone else," Kallas added.
NATO members Turkey, Bulgaria and Romania meanwhile on Thursday signed an agreement in Istanbul on demining the Black Sea to ensure safe waters once the war is over.
The Russian navy mined Ukraine's Black Sea coastline in the early stages of its invasion nearly two years ago.
Zelensky appealed for badly needed air-defence systems when he began his tour on Wednesday in Lithuania, warning that Western hesitation on aid for Ukraine was emboldening Russia.
As he spoke of a "delay" of the Western aid packages, Zelensky said it was "impossible to survive" without fresh military support.
He is expected to travel to Latvia later on Thursday, the third leg of his first foreign trip abroad this year.
