"General Kellogg, a meeting which restores hope. We need strong agreements that will really work. I gave instructions to work fast and in a very, very even-handed fashion," Zelenskiy said in his nightly video address on Thursday.
"The details of the agreement are important. The better the details are drafted, the better the result."
The meeting with Kellogg took place a day after Zelenskiy and US President Donald Trump exchanged barbs as US-Russian talks got under way in Saudi Arabia on ending the three-year-old war pitting Kyiv against Moscow.
Ukraine was not invited to the talks.
After the meeting with Kellogg, Zelenskiy said on social platform X that Ukraine had to "ensure that peace is strong and lasting - so that Russia can never return with war".
"Ukraine is ready for a strong, effective investment and security agreement with the President of the United States.
"We have proposed the fastest and most constructive way to achieve results. Our team is ready to work 24/7."
The talks with Kellogg also followed Ukraine's rejection of an initial US proposal to develop rare earths in Ukraine.
Zelenskiy had earlier struck a conciliatory tone after accusing Trump of repeating Russian disinformation in response to the US president's accusation that Ukraine had started the three-year-old war with Russia.
Trump went on to refer to Zelenskiy as a "dictator" who should act fast or lose his country.
Trump, in office for just a month, is pushing for a quick deal to end the war and has alarmed Washington's European allies by leaving them and Ukraine out of initial talks with Russia.
His vice-president, JD Vance, said on Thursday he believed that an end to the conflict was near and there was no stopping the war without speaking to Russia.
US National Security Advisor Mike Waltz, meanwhile, told a White House media briefing that Zelenskiy's insults were unacceptable and the Ukrainian president needed to go back to the table and discuss a previously floated deal to give the United States access to Ukraine's minerals resources.
Kellogg had arrived in Kyiv on Wednesday and said at the time he was there to listen.
A planned joint media conference was cancelled at the US's request, Zelenskiy's office said.
Trump is seeking to re-establish ties with Russia and also invest in Ukraine's mineral resources critical to the energy transition.
Ukraine rejected an initial US plan as it did not include security guarantees.
European leaders have responded to Trump's stance on Ukraine by pledging to step up spending on defence and some are considering a US-backed European peacekeeping force for the country.
French President Emmanuel Macron, who is due to meet with Trump in Washington on Monday, said on Thursday he would tell Trump not to be "weak" on Russian President Vladimir Putin.
"How can you be credible with China if you're weak with Putin?" Macron said during a question-and-answer session on social media.
Waltz, for his part, said the US would welcome European-backed security guarantees for Ukraine, and he pushed for all NATO members to spend at least two per cent of their GDP on defence by the alliance's next summit, set for June.
The Kremlin says the European plan is a major cause for concern but Zelenskiy and NATO have welcomed it.
"It is vital that ... Russia will never again try to take one more square kilometre of Ukrainian land," NATO Secretary-General Mark Rutte said.
Russian forces have laid Ukrainian cities, towns and villages to waste, and Moscow controls a fifth of Ukraine and claims ownership of more.
Ukrainian officials say a ceasefire would just give Russia time to prepare for further aggression.
However, the head of Ukrainian military intelligence agency said on Thursday there could be a ceasefire in 2025, while casting doubt on its durability.
