David Cameron has told Tunisia's prime minister he hopes to lift advice against British nationals visiting the Mediterranean holiday destination "as quickly as possible".
The Prime Minister spoke with Habib Essid for the first time since last month's gun attack on holidaymakers in the beach resort of Sousse which left 38 dead, including 30 Britons.
Mr Essid - who previously said he regretted Britain's decision to evacuate tourists from his country - told Mr Cameron he "understood" why the UK advised its nationals to leave.
Around 3,000 UK holidaymakers are thought to have flown home from the north African country following last week's Foreign Office warning that a terrorist attack was "highly likely". The evacuation of UK tourists came as a hammer blow to Tunisia's tourism industry, which makes up around 15% of the country's GDP.
Downing Street said the 10-minute phone call "was an opportunity to talk about how we keep working together to tackle the terrorist threat and the shared challenge we both face from extremism".
"The Prime Minister said to the Tunisian prime minister that Britain stood with Tunisia on its road to democracy and wanted to redouble our joint efforts to counter terrorism, and that notwithstanding the decision we had to take on travel advice, we remain absolutely committed to continuing our efforts to work with them on counter-terrorist co-operation and security.
"Tunisia's prime minister welcomed this support and said he understood why the UK had to take the decision it took last week, and looked forward to working together on these issues in the future.
"Both agreed the shared objective was to put in place the right security measures and to look at ways to counter the terrorist threat in Tunisia, such that we would be able to change our travel advice as quickly as possible."
Mr Cameron spoke to Tunisia's president Beji Caid Essebsi in the immediate aftermath of the attack.
The latest phone call, which was requested by Mr Essid, came as the funeral took place in Perth of Billy and Lisa Graham, who were among those murdered by gunman Seifeddine Rezgui in Sousse on June 26.