U.S. Secretary of State Antony Blinken addressed concerns Wednesday that the U.S. deal to release five Iranians and agree to the release of nearly $6 billion in frozen Iranian assets — in exchange for the release of five Americans who were detained in Iran — encourages hostage-taking among hostile nations. 

"These are hard decisions, hard decisions for the president to make," Blinken, who is currently in New York for the U.N. General Assembly, told "CBS Mornings." 

But Blinken said over 30 Americans who were unjustly detained worldwide are now home as a result of those decisions.

Some Republicans voiced opposition to the exchange, saying financial relief in a hostage situation will incentivize future hostage-taking.  

Blinken said it's important "that we do what we're doing" — "going after any of those that we find who are involved in unlawfully detaining Americans with sanctions, with restrictions on their travel." He also said officials are working with international partners to discourage the practice of taking hostages for political purposes.

"We're bringing, along with Canada, a number of countries together to try to establish much more clearly an international law that the practice of taking people, using them in fact as political hostages, is absolutely unacceptable. And also, getting countries to say, 'If you take one of our people, then all of us together will come down on you,'" Blinken said.

"People are not going to want to set foot in those countries if they know they can be thrown in jail for no reason," said Blinken. 

The Americans who were freed include three who were imprisoned after they were sentenced on unsubstantiated charges of spying. The Americans boarded a Qatari plane in Tehran on Monday that flew to Doha and were transferred to U.S. custody. They arrived in the Washington, D.C., area, on Tuesday morning. 

As part of the deal, the U.S. agreed to help Iran access $6 billion in Iranian oil assets that were held in a restricted account in South Korea. The money was being transferred to an account in Qatar, and the Biden administration has said the U.S. will monitor the Qatar account and restrict the use of funds for humanitarian purposes. Blinken noted the released money does not include any U.S. tax dollars.

"We made an arrangement with the bank in question, this is a bank in Qatar, to make sure that we would have clear visibility over the way the money is spent," Blinken said. "And if it's not being used for humanitarian reasons, it's not being spent for food, medicine, other things, it'll get shut down."

On Ukraine, Blinken said the recent dismissals within Ukraine's defense ministry due to corruption concerns demonstrate President Volodymyr Zelenskyy and other Ukrainians are taking the matter seriously. He said the U.S. has teams in Ukraine that work to ensure that aid money is being used for its intended purposes.

President Biden is asking Congress to approve an additional $24 billion in aid to the country.

"I've talked to members of Congress who've gone to Ukraine, and they've seen what we're doing to make sure the money is well accounted for. They come back very impressed with these controls, with these measures. And they've told us that they haven't seen anything as effective in other places in the past where we supported countries who are being the victims of aggression," Blinken said.