The ATP has warned players about security concerns at its tournament in Acapulco, Mexico, and has been reassured by Mexican officials that steps are being taken to ensure safety at the largest tournament in Latin America.
The Mexican Open begins on Monday as a combined ATP and WTA event.
The Pacific resort city has been hit by a wave of drug violence in Mexico, although little of the violence happens in tourist areas.
In January, the bodies of 14 men with their heads chopped off were found outside a shopping center. A 15th body with its head intact was also found nearby.
The ATP, in a statement sent to The Associated Press, said it had received assurances from all levels of the Mexican government.
"Following an independent security assessment and discussions with tournament organizers, we are satisfied that responsible measures are being taken, and that the event has the full support of the authorities of Acapulco, the state of Guerrero, and the Mexican federal government," the statement said.
Players have received e-mails from the ATP about the situation, cautioning them about going out and suggesting that they should stay near their hotel. It's also been suggested that they arrive as late as possible and leave once eliminated.
Tournament organizers have played down the security concerns, pointing out that the International Olympic Committee and President Jacques Rogge held their executive board meeting in the coastal resort in October.
David Nalbandian said Saturday he was thinking about withdrawing since he already has a groin injury and could use the rest before Argentina's Davis Cup match against Romania from March 4-6.
Tournament director Raul Zurutuza later confirmed Nalbandian's withdrawal.
"It's a great and enjoyable tournament to play," said Nalbandian, who lost to Tommy Robredo in the quarterfinals of the Copa Claro in Buenos Aires on Saturday.
"But for right now it's a little more difficult because of the security situation. We (players) are a bit scared about this and we're trying to decide what to do."
Zurutuza said the danger was being exaggerated and complained about communications from the ATP and the WTA, which will also play a Mexico tournament.
"It is being blown out of proportion - what is going on, that we are concerned about the violence," Zurutuza said. "We are. But in the context of tennis being played, I believe a great week awaits us."
Spanish player David Ferrer, winner of the last Acapulco tournament, downplayed the danger.
"I think things are being greatly exaggerated," Ferrer said. "We tennis players have all the guarantees" for personal safety.