Foreign Secretary Philip Hammond has made an unannounced visit to Libya in a show of support for the country's new UN-backed national unity government.
Mr Hammond was taken amid tight security to the heavily-protected naval base where the nine-strong administration of prime minister-designate Fayez Serraj is struggling to establish its authority.
His arrival follows similar visits over the past week by the Italian, French and German foreign ministers while the British ambassador also returned to the city for the first time since most foreign embassies pulled out in 2014 as it was considered too dangerous to remain.
The Foreign Secretary said the UK was committing £10 million in further assistance for the fledgling government of national accord (GNA).
The package includes £1.8 million for counter-terrorism operations and £1.5 million for combating the people traffickers smuggling migrants across the Mediterranean into Europe via Libya.
"Britain and its allies fully support Prime Minister Fayez Serraj and his government as they restore peace and stability to the whole of Libya. We stand ready to provide further assistance to Libya and its people," he said.
"Britain is at the forefront of the international community's efforts to stabilise Libya and is committing an extra £10 million to help the government of national accord strengthen political institutions, the economy, security, and justice.
"This fund builds on our existing support to Libya of £12 million last year for development and humanitarian assistance.
"I welcome the continued efforts of Prime Minister Fayez Serraj and members of the presidency council to make progress on security, rebuilding the economy and restoring public services for the benefit of all Libyans."
Mr Hammond also went to listen to Libyan requests for additional assistance in strengthening their armed forces, which are tasked with establishing security after five years of strife dominated by warring militias.
At the same time the West is anxious to see the new government take on Islamic State (IS), which has established a foothold in Sirte - the home town of former dictator Muammar Gaddafi - from where it has launched a series of suicide bombings and attacks on oil facilities.
Ministers have indicated that the UK is ready to help train Libyan armed forces for operations against IS.
But while it is believed that a small number of special forces troops are already in the country, British sources have played down suggestions the UK is about to deploy a 1,000-strong training mission as part of an international assistance force of 6,000.
One source said they would want to see the GNA up and running, with properly functioning ministries, before making any commitment of that nature.
"We need a functioning government running ministries to decide what they need to do. We are months and months away from any kind of decision of that kind," the source said.
The precarious nature of Mr Serraj's putative new government was underlined when he and his team were forced to sail into Tripoli when they arrived in March because the authority controlling the capital refused to allow them into its airspace.
But while Mr Serraj has been able to rally support from the Tripoli militias and the municipal councils of western Libya, a rival administration in the eastern city of Tobruk has so far refused to recognise the GNA.
The Europeans meanwhile are looking to the GNA to allow the EU's Operation Sophia against people traffickers to extend its naval patrols into Libyan territorial waters.
The move follows the effective closure of the migrant trail through Turkey and Greece, prompting fears of a new wave of people trying to reach Europe via Libya.
Following his talks in Tripoli, Mr Hammond was heading to Luxembourg for a meeting of EU foreign and defence ministers to discuss the situation in Libya - including a video conference with Mr Serraj.