* Turkey plans to deploy troops to Libya to help Tripoli
* Forces of General Haftar trying to seize capital
* Bill warns of threat to Turkish private investments
* Syrian fighters would be latest foreign arrivals
* Syrian rebels deny Ankara requested to send fighters to Libya (Adds Free Syrian Army source, spokesman comments)
By Orhan Coskun
ANKARA, Dec 30 (Reuters) - Turkey is considering sending allied Syrian fighters to Libya as part of planned military support for the besieged government in Tripoli, senior Turkish sources said on Monday, potentially bringing more foreign influence into the complex conflict.
President Tayyip Erdogan said last week Turkey would deploy troops to Libya after Fayez al-Serraj's internationally-recognised government requested support to fend off an offensive by General Khalifa Haftar's eastern forces.
The move is meant to protect Turkish private investment in Libya and bolster its energy claims in the Mediterranean, but could also put Ankara at odds with other foreign players in the war.
Two senior Turkish government officials and two security officials, who spoke to Reuters on condition of anonymity, said Ankara had not yet deployed any Syrian fighters to Libya.
"But evaluations are being made and meetings are being held on this issue, and there is a tendency to go in this direction," said one official, adding no decision had been made on numbers.
Turkey-backed Syrian fighters spearheaded a Turkish military incursion into northeast Syria in October targeting a Kurdish militia. Ankara, which opposes President Bashar al-Assad, also backs Syrian rebels in the northwest province of Idlib in Syria's nearly nine-year civil war.
It was unclear whether Ankara was mulling sending Syrian fighters as part of a first deployment into Libya.
Haftar's forces - supported by Russia, Egypt, the United Arab Emirates (UAE) and Jordan - have failed to reach the centre of Tripoli. But they have made small gains in recent weeks with the help of Russian and Sudanese fighters, as well as drones shipped by the UAE, diplomats say.
The Syrian Observatory for Human Rights, a monitor, cited sources saying 300 Turkey-backed Syrian fighters had been sent to Libya while others were training in Turkish camps.
However, a spokesman for the Turkey-backed Free Syrian Army (FSA) on Monday denied that Ankara had made a request to send FSA fighters to Libya.
A military source within the FSA said the FSA was not being deployed to Libya, but that Syrian fighters in Syria and Turkey had signed up on an individual basis, for a salary, to work as "bodyguards" for a Turkish security company to protect bases and headquarters which Turkish forces will use in Libya.
Turkey's military has been involved in Syria since 2016.
"The military's experience abroad will be very useful in Libya. However, there is the possibility of using the experience of Syrian fighters as well," said one of the security officials.
"After parliament accepts the mandate, a step may be taken in this direction," the person added.
Ankara signed two accords with Libya's government last month: one on security and military cooperation and another on boundaries in the eastern Mediterranean.
The maritime deal ends Turkey's isolation at sea as it ramps up offshore energy exploration that has alarmed Greece, Cyprus and others. The military deal would preserve its lone ally in the region, Tripoli, and protect investments by construction firms and other Turkish companies.
Foreign Minister Mevlut Cavusoglu has said Turkey aims to prevent Libya sliding into chaos. Erdogan, who discussed the Libyan conflict with his Tunisian counterpart last week, has said a ceasefire in Libya must be set as soon as possible.
The deployment bill was sent to parliament on Monday, prompting the main opposition party to reject it on grounds it would exacerbate conflict.
The bill's text warned that Haftar's army has threatened Turkish companies in Libya and Turkish ships in the Mediterranean.
"Turkey's interests ... will be negatively impacted if attacks by the so-called Libyan National Army are not stopped and clashes become a severe civil war," it said.
Turkey exported $1.5 billion in jewellery, furniture, poultry and other goods to Libya last year, more than quadruple the imports of mostly metals from the North African country.
Construction firms including Ustay Yapi, Tekfen and Guris Insaat dominate the Turkish-Libya Business Council's board, highlighting the sector's interests there.
Mega-infrastructure projects have driven the Turkish economy's mostly booming 17 years under Erdogan. (Additional reporting by Ceyda Caglayan and Ali Kucukgocmen in Istanbul, Tuvan Gumrukcu in Ankara, Eric Knecht in Beirut and Khalil Ashawi in Syria; Writing and additional reporting by Jonathan Spicer; Editing by Andrew Cawthorne and Ed Osmond)