While Wall Street is concerned over reports of Twitter’s slowed user growth, Twitter CEO Dick Costolo is optimistic.

“We had re-accelerating user growth in our biggest market, the U.S., in [the first quarter]. So I feel great about the growth that we’re driving into the platform via the roadmap changes we’re making,” Costolo said Monday on “CBS This Morning.”

Last week the social media giant announced first quarter revenue of $250 million. Since then, however, Twitter’s stock price dropped over 8 percent, and for the year, it is down over 42 percent.

“The 3.3 billion views of the tweets about the Oscars in just the 48 hours after the Oscars shows the incredible reach and distribution of the platform,” Costolo said. “So we’re working on transforming that reach and impact into the logged-in experience, and I feel really good about the roadmap we’ve got to do that.”

One of the transformations for the Twitter user is an “in-the-moment commerce” experience through its partnership with Amazon.com.

“When we talk about ‘now commerce’ and real-time commerce — if somebody tweets something with a link to Amazon, and you reply to that tweet and just say ‘#AmazonCart,’ we’ll put that item in your Amazon cart once you connect your Twitter account to Amazon,” Costolo said. “So that notion of seeing something that somebody talks about and then just saying, ‘I want that, I want to put it in my Amazon cart,’ you can do that now with ‘in the moment’ commerce.”

Costolo, who has been CEO since October 2010, will be awarded the inaugural PEN/Toni and James C. Goodale Digital Freedom Award Monday for Twitter’s “contribution of a powerful new tool for communication and expression to hundreds of millions of people worldwide.”

Costolo said Twitter’s reach has been embedded into the culture of the world and is “so much bigger than any one product.” One of the biggest impacts Twitter had on international movements was during the Arab Spring when many protesters used it as a tool for communication and coordination.

There are countries still today that have banned or tried to shut down Twitter, including Turkey.

“We were shut down briefly in Turkey. The constitutional court there said that we needed to be turned back on, and we weren’t turned back on. I think that we continue to talk to the government in Turkey and work with them. … Obviously we need to make sure we abide by the rule of law and the countries in which we operate,” he said. “And as long as we have appropriate legal request for the content that those countries have concerns with, we’ll act on those.”

Other countries that have blocked Twitter include Iran, Pakistan, Egypt, North Korea and China. The Chinese use Weibo as an alternative to Twitter, but Costolo does not see them as a competitor.

“I think that when we think about Twitter and services like Weibo in China, we think of our platform as truly being global and growing really around the world, as opposed to any one local or regional player competing with us,” he said.

With some in the media writing eulogies for Twitter, Costolo said news of Twitter’s decline are exaggerated.

“It’s been the case since the company was founded in 2006, and frankly, for a number of companies in the Valley that people are constantly saying, ‘It’s over for so-and-so,'” Costolo said. “Then they say it six months later, and again a year later and a year later and a year later. So that’s been something we’ve heard and other companies in the Valley for quite some time.”