MANILA - Islamist militants in the southern Philippines have said they are willing to extend Friday's deadline to execute one of two German hostages by two hours if they receive word that ransom will be paid.
A senior military officer in the region said negotiations with the Abu Sayyaf militant group were on, but he did not know of any details.
"What I can tell you is we are ready to conduct operations, specifically for law enforcement operations, not necessarily for rescue," Rear Admiral Reynaldo Yoma told Reuters by telephone.
"If we plan to do a rescue, that might derail ongoing negotiations," he said.
The Abu Sayyaf, which says it supports Islamic State fighters in the Middle East, had earlier threatened to kill one of the two hostages at 0700 GMT on Friday on the remote southern island of Jolo.
They want a ransom of 250 million Philippine pesos (S$7 million) and have demanded Germany stops supporting US-led air strikes in Iraq and Syria.
The group, which has a record of kidnappings, killings and bombings in the past, called a radio station in Zamboanga city to reiterate its demands as the Philippines stepped up army patrols on Jolo, a hotbed of Islamist militants in the mainly Catholic country.
The Abu Sayyaf has long been based in the interior jungles of the island, which is about 960 km (600 miles) south of Manila in the Sulu Sea, midway between the Philippines and eastern Malaysia.
"We are willing to extend the deadline for two hours if we get a call that ransom will be paid," Abu Rami, a spokesman for the Abu Sayyaf, told the Radio Mindanao Network in a telephone call.
The group has used the radio station for its previous contacts with authorities.
The German man, who spoke briefly in the same call to the radio station, recalled how he and a female companion were taken hostage while on a holiday near the southern island of Palawan.
He said life in the jungle was hard and it was taking a toll on his health.
A spokeswoman for the German foreign ministry has said that "threats are no appropriate way of influencing German foreign policy", and that the ministry's crisis group was working on the case.
Lieutenant General Rustico Guerrero, a Philippines' military commander, said the government was closely monitoring the situation on the ground.
"We know the general area where they are. We are aware of the demands and situation but this all we can say. We don't want to put the lives of the hostages in jeopardy," Guerrero said.
The German man, who is a doctor, and the German woman were seized by the Abu Sayyaf group in April when their yacht broke down near Palawan en route to Sabah in eastern Malaysia.
It is not clear if the militants, who claim they want an independent Islamic nation in the south but are known for kidnap-for-ransom raids, have contacts with Islamic State.
Some Muslim groups in the southern Philippines have long been fighting Manila's rule, but Abu Sayyaf burst into prominence in 2000 after kidnapping 21 tourists and workers from a dive resort in nearby Malaysia.
They held the hostages, who included French, German, Finnish and South African nationals, for months on Jolo before freeing them for millions of dollars in ransom paid by then Libyan leader Muammar Gaddafi, according to Philippine officials.
Libya denied it paid a ransom but acknowledged government officials were involved in negotiations.
Several of the hostages visited Tripoli after their release.