Jordan will face Austria, Algeria and Argentina in Group J at the June 11th to July 19th World Cup and are holding their final training camp in Antalya this week.
Media access to training sessions has been tightly restricted as the team fine-tuned tactics.
Some players say they can barely sleep in anticipation of the tournament but Sellami wants them to draw confidence from Morocco's achievement at the last World Cup, where they lost 2-0 to France in the last four.
"In big competitions, many teams can surprise. My country Morocco reached the semi-finals in the last World Cup," he said. "That gives us belief."
Jordan will play Costa Rica later on Friday and Nigeria on Tuesday as part of a four-team regional tournament that also includes Iran and was relocated from Jordan to Turkey due to the war in the Middle East.
"Of course we feel sad about what is happening. I hope there will be peace," midfielder Noor Al-Rawabdeh said at the camp.
"But this is football — we moved here and we need to adapt. In the World Cup you face the unknown, so we must be ready for everything."
Despite their underdog status, the players say they are not going to the World Cup just to make up the numbers.
"For us, we are not going just for participation," Al-Rawabdeh added. "We are aiming to go as far as we can in the tournament.
"To be honest, sometimes we don't sleep when we think about it," he added. "It’s a dream come true for us."
Jordan secured an automatic berth at the World Cup after finishing second behind South Korea in their Asian qualifying group.
Defender Mohammad Abu Alnadi said the squad were relishing the opportunity to compete on football's biggest stage.
"It's truly amazing. All of us are excited. It's one of the highest levels any player can play," he said.
"We want to go as far as possible — like any other team — and make history again."
Sellami said the Antalya camp was a key stage in building experience ahead of facing elite opposition.
"We are preparing step by step. We've played against different football cultures," he said.
"We are collecting experience and, Inshallah (God Willing), we will surprise many people."