* Rescue ship docks after security concerns force two-day delay
* Will pick up 200 migrants, not 300, because of dwindling supplies
* IOM asks all parties to allow safe passage to the port (Updates with migrants boarding ship)
GENEVA, Aug 25 (Reuters) - About 200 foreigners desperate to leave Tripoli began boarding a rescue ship on Thursday after worries about security in the Libyan capital delayed their evacuation for two days.
The International Organization for Migration (IOM), which chartered the vessel, said security conditions in and around the port had improved enough for the operation to go ahead, allowing the ship to dock at Tripoli port on Thursday.
"It has not been easy to do this operation. We never expected it to be. Nevertheless, there is a huge sense of relief that all our efforts are in the end helping these migrants," Pasquale Lupoli, IOM Regional Director for the Middle East and North Africa, said in a statement.
"However, IOM reiterates its call to all parties to allow migrants safe passage to the port. This issue remains a major challenge in any further evacuations of migrants from Tripoli."
The evacuees expected on board include Egyptians, Filipinos, Canadians, Algerians, Moroccans and an Italian.
"Some migrants have already got to the port," IOM spokeswoman Jemini Pandya told Reuters.
The evacuation mission also faced the possibility of delays because of the difficulty of getting the evacuees safely to the port from their embassies and homes, crossing checkpoints in what has been a war zone over the last 48 hours.
"Fear of fighting, looting, sniper fire and checkpoints prevents migrants from leaving their homes to reach the port area, the only place from which they would be able to flee the country," the IOM statement said.
Although the ship has space for 300 evacuees, it will only pick up about 200 because the two extra days spent at sea have cut supplies of food and water on board, and it would be difficult to restock in Tripoli, Pandya said.
The boat, which has IOM medical staff on board, will leave for Benghazi later on Thursday, and a second ship with capacity of around 1,000 passengers is expected to carry out another evacuation at the weekend.
The IOM said more than 5,000 people had asked to be evacuated as the fighting closed in on Tripoli over the past few weeks. But when the ship arrived, Libya's National Transitional Council told it not to dock because conditions were too dangerous.
The IOM has said some of those who had asked to be rescued might change their minds if the security situation improved, since many were long-term residents with stronger ties to Libya than to their own countries.
The IOM has evacuated 30,000 foreigners in the past six months, including 10,000 from Tripoli. The evacuees leaving on Thursday will go to a transit centre in Benghazi before being taken to Salloum on the Egyptian border and given help to return to their home countries.
(Reporting by Tom Miles; Editing by Rosalind Russell)
Our Standards: The Thomson Reuters Trust Principles.
