The world and European champions top Group I by six points with a 100 percent record from four games after coming back to beat their closest challengers, the Czech Republic, 2-1 at home on Friday.
They visit the Baltic nation, however, with concerns over the playing surface at the Darius and Girenas stadium, which has barely any grass on it after a harsh winter.
"From the pictures we have seen it reminds me of the dirt pitches we used to play on when we were young," Andres Iniesta, the scorer of Spain's winner in the World Cup final last year, told a news conference on Sunday.
"Whether to play or not isn't our decision, that's up to the referee and UEFA. Obviously they aren't the best conditions, but if we have to play we will be ready to do so."
Spain beat Lithuania 3-1 in Salamanca last October but had to work hard to open up their visitors, all three goals coming in the second half.
"They're a team who stick to you and don't let you breathe," Iniesta said. "They defend from deep, which is habitual from many teams now. We are away from home, in conditions which perhaps aren't the best...it will be tough."
A decision with regards to the pitch is expected to be taken on Tuesday, the Lithuanian soccer federation has said.
The hosts, fourth in the group with four points from three games, warmed up with a 2-0 friendly win over Poland in the same stadium on Friday, using a system coach Raimondas Zutautas hoped to use against Spain.
"The team implemented a game plan very well on Friday by counter-attacking on the wings," Zutautas told Reuters by telephone.
"We don't need any special motivation for the match against Spain, it's already enough that we will be playing against world champions.
"We would be happy to win or draw, but we would not be very disappointed if we lost."
Lithuania defender Marius Stankevicius, who plays for Spanish side Valencia, was apologetic about the state of their pitch.
"I am sad about the conditions in which we are receiving teams such as Poland and Spain," he said. "It's a shame for Lithuania."
Lithuania: 1-Zydrunas Karcemarskas; 23-Marius Stankevicius, 5-Andrius Skerla, 3-Ramunas Radavicius, 4-Tadas Kijanskas; 7-Mindaugas Panka, 8-Edgaras Cesnauskis, 2-Deividas Semberas, 13-Saulius Mikoliunas; 10-Darvydas Sernas, 9-Tomas Danilevicius.
Spain: 1-Iker Casillas; 17-Alvaro Arbeloa, 15-Sergio Ramos, 3-Gerard Pique, 11-Joan Capdevila; 22-Jesus Navas, 8-Xavi, 14-Xabi Alonso, 16-Sergio Busquets, 6-Andres Iniesta; 7-David Villa.
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