Volodymyr Zelenskyy has rejected claims the war with Russia is at a "stalemate".
In an exclusive interview with Sky News' US partner NBC News, the Ukrainian president acknowledged Kyiv's progress had been slow and said there was "fatigue" with the conflict.
But he insisted his military was "still more motivated than any Russians who came to Ukraine to kill us".
As the war between Israel and Hamas has escalated, there has been concern in Kyiv that aid to Ukraine would suffer.
Recognising the war means allies are providing funding and resources in two conflicts, Mr Zelenskyy sought to align his country's fight against Russia with Israel's battle against Hamas.
He accused Russia of playing a role in both wars by sponsoring Hamas, adding that the "whole world should do all they can to stop this war" in the Middle East.
Ghazi Hamad, a senior member of Hamas's political bureau, denied any links with Moscow in an interview last week with NBC News.
However, he noted Hamas leaders have talked with representatives from Russia, China and "different countries".
Mr Zelenskyy rebuffed recent suggestions from US military officials and Ukraine's own commander-in-chief that the war was entering an impasse after 20 months of fierce fighting.
"They thought they would checkmate us, but this didn't happen," he said.
"I don't think that this is a stalemate."
His remarks contrast with those of General Valeriy Zaluzhnyi, who told The Economist last week that "there will most likely be no deep and beautiful breakthrough" despite the counteroffensive launched in June.
Mr Zelenskyy told NBC's Meet the Press programme he was "ready to go to Israel today", although attempts by the Ukrainian leader to visit the country have stalled.
"It is difficult to say because I'm a president of a country at war, and you know that on our battlefield it's very hot," he said, adding that any possible visit would depend on "what's happening on the battlefield" in Ukraine and whether it's possible to get Ukrainian citizens "stranded" in Israel back home.
Mr Zelenskyy reiterated his calls for more air defence systems from the US and other allies, saying Ukraine particularly needs drones that can attack and gather intelligence.
Without such help, Ukrainians would find it difficult to "step forward", he said.
"We need to save our country. That's why one of the ways is to co-produce air defence," Mr Zelenskyy said.
"But during this time, during our co-production, our message to the world, to the United States, to Europe, to Asia: to give us some air defence systems, just to use them, just to rent them, rent for this period, especially winter. Winter [is a] very challenging period."
He said it was important for allies to continue their support of Ukraine, because Kyiv is defending "joint values" such as democracy.
By contrast, he said, he believed Vladimir Putin wants to "divide Europe, to weaken the United States of America, and he always wants to find a hot spot in Europe so that there is no stability in Europe, in the Middle East".
"It's very important not to lose the will, not to lose this strong position, and not to lose your democracy," Zelenskyy said, adding: "We wanted your support, like we say, yesterday."