Lionel Messi produced some moments of magic in Buenos Aires, but the hosts were unable to break through in the 0-0 draw.
The result left Argentina in sixth – outside the qualification spots – in CONMEBOL qualifying, ahead of a trip to Ecuador on Tuesday.
"I am still confident that we will be at the World Cup," he told a news conference.
"Today was a very good game. We just missed a goal. I am very hopeful and excited about what is coming.
"The team never gave up, put in a huge effort and deserved another result."
Sampaoli praised Messi for his performance, with the Barcelona star unfortunate to have scored just four goals in nine qualifiers this campaign.
"Messi played a great game, created chances and gave good passes," he said.
A win over Ecuador will be enough for Argentina to secure at least a place in a play-off.