Spokesman Sean McCormack said the package of reforms approved on May 18 also included "a whole host of other political reforms," aside from one allowing President Nursultan Nazarbaev to stay in office for life.
"It's a step, ultimately, when you look at the balance of these things, in the right direction," McCormack said, adding, however, that the pace of political reform was not as quick as Washington would have hoped.
"Is it all that the rest of the world would like to see? No, it's not. But again, this is a country that we're -- we have high hopes for, that we're working closely with, they have a lot of potential," he said.
The changes exempt Nazarbaev from a bar on holding the post for more than two terms in a row, though Nazarbaev has not indicated he will run for reelection when his term expires in 2012.
Other amendments transfer some power from the presidency to the parliament after 2012.