(CNN) -- Several U.S. navy ships have converged near a Ukrainian cargo ship, seized last week by pirates off the coast of Somalia, a navy official told CNN Monday.
A photo from the USS Howard shows Somali pirates in small boats hijacking the MV Faina last week.
Lt. Nathan Christensen said the ships, including the USS Howard, were working toward the safe release of the seized ship, which is loaded with Soviet-era tanks and weapons.
The navy ships were not involved in negotiations between the pirates and the shipping company, he said.
"There are now several U.S. ships keeping vigilant watch," he said. "We want the crew to remain safe and for the cargo not ot fall into the wrong hands."
A Russian frigate was also reported to be on its way to the area.
"This is an international problem that requires an international solution," Christensen said, when asked to respond to the reports.
The pirates, who Christensen said were "loitering on and around the ship," have lowered their ransom demand from $35 million to $20 million.
Andrew Mwangura of the Kenya-based Seafarers Assistance Programme told CNN Monday that the organization's sources in Somalia reported the change in the ransom amount.
The pirates hijacked the ship Faina off the coast of Somalia on Thursday. The ship was headed to the Kenyan port of Mombasa after departing from Nikolayev, Ukraine, and was seized not far from its destination.
The Kenyan government said Sunday it had not been contacted by the hijackers.
Rashid Abdi, an independent Horn of Africa analyst with the International Crisis Group, said the pirates have been making their ransom demands in interviews with media outlets.
"The pirates are very clever and well connected," Abdi said. "They know the importance of using the media to put forward their side of the story."
Alfred N. Mutua, a spokesman for the Kenyan government, warned the media to be cautious about "being used by terrorists who, on realizing they cannot get away with their plunder, are trying to draw attention from their criminal acts."
"Do not empower them by giving them the publicity they seek," he told CNN.
Faina is owned and operated by Kaalbye Shipping Ukraine, and its crew includes citizens of Ukraine, Russia and Latvia, the Navy said.
Abdi Salan Khalif, commissioner of the coastal town of Harardhere, told CNN the pirates told a group of town elders that one crew member died of high blood pressure problems. Watch report on dead crewman »
The Ukrainian ministry said the ship is carrying 33 Soviet-made T-72 tanks, tank artillery shells, grenade launchers and small arms. Ukraine sold the weapons to Kenya, said Ukraine Defense Minister Yuri Yekhanurov, according to the Interfax-Ukraine news agency.
CNN's David McKenzie contributed to this report