The American entourage arrived in the capital Kyiv under great secrecy on Sunday for a meeting with Volodymyr Zelensky.
Journalists were not allowed to report on the visit until Blinken and Austin left Ukraine and were safe in southeastern Poland, reports AP.
Only early on Monday morning, Swedish time, did the United States confirm that the meeting had been held and its contents.
In the talks in Kyiv, Blinken and Austin promised a package of military support worth 713 million dollars, equivalent to almost seven billion kronor.
The money will go to Ukraine and another 15 allied countries that help Ukraine militarily, including NATO members.
Just over SEK 3 billion is earmarked directly for Ukraine.
The new addition means that the United States has contributed a total of SEK 37 billion in military support to Ukraine since Russia's invasion began, according to the White House.
"We will continue to support Ukrainians in their fight to defend their homeland," US President Joe Biden wrote on Twitter on Sunday night.
Blinken also told Zelensky that US diplomatic personnel, who are usually stationed in Ukraine, will begin returning and making day trips from Poland to Lviv.
A new US ambassador will also be appointed in Ukraine.
First meeting since the war
Before the meeting, Zelensky said that he expected concrete messages from the United States that Ukraine would receive more weapons that the country had requested.
- You can not come empty-handed and we do not just expect gifts or some kind of cake, we expect specific things and specific weapons, he said.
It is the first time since the war broke out that Zelensky has met a US government official face to face.
The last time was on February 19, five days before the start of the Russian invasion, when he met with Vice President Kamala Harris in Munich.