The State Department cannot conceive of Iran using American hostages as "cash cows" in the wake of the January 2016 deal in which American prisoners in Iran were released on the day the United States paid the Islamic Republic $400 million in cash.

State Department spokesman John Kirby was asked about Robin Shahini, an Iranian-American student who has been detained in Iran since July and was sentenced Monday to 18 years in prison. He had traveled to Iran to visit his mother, who has been diagnosed with Alzheimer's Disease. Shahini has dual citizenship, however, which Iran does not recognize. The State Department called on Iran to end politically motivated detentions and to protect human rights in response to Shahini's sentencing.

After Shahini's case was discussed, reporters asked Kirby about Americans being held by Iran and the appropriate response.

"This keeps happening, over and over and over again," Associated Press reporter Matt Lee said before asking if Secretary of State John Kerry continues to talk to this Iranian counterpart about this issue, which Kirby said he does.

"I realize that you guys are insistent and make a case, make an argument that the sequencing of what happened in terms [of] January and the release of the U.S. prisoners, [the] return of the money to Iran, that that money was not a ransom," Lee said. "But given the fact that this keeps happening, Iranian-Americans keep being arrested and keep being convicted in Iran, has it occurred to anyone here that, despite your best efforts to convince the Iranians and the rest of the world that these payments weren't ransom, that in fact they regard them as ransom and [the payments] have had the effect of this kind of thing continuing to happen?"

Kirby answered that he cannot speak for what the Iranians may think, again denying that the payments were ransom.

"What may be behind this I don't think any of us known with certainty," Kirby said.

"Are you at least able to conceive of the idea that an Iranian perception, if in fact there is one, a perception in Iran that they successfully took and held Americans, then released them and at the same time received millions and millions and millions of dollars in cash, that their perception of that being perhaps ransom is contributing to what is the continued arrest and conviction of American citizens in their country?" Lee asked.

Kirby again said that he could not speak for what the Iranians may think and denied that the United States paid ransom.

Another reporter pointed out how Iran currently wants a $4 million payment for another individual, a permanent resident of the United States, to be released, saying it goes to Lee's point that Iran sees Americans as "cash cows." Kirby said that he had not seen the report about Iran wanting a $4 million ransom payment.

When Lee asked Kirby if the United States was going to engage in any more prisoner swaps with Iran for money, Kirby would only say that the U.S. does not pay ransom.

Kirby also said there is no need to strengthen the State Department's travel warnings to American citizens.