Britain and Japan today formally signed a trade agreement, marking Britain's first big post-Brexit deal on trade, as it continues to struggle to agree on a deal with its closest trading partners in the European Union. 

Britain formally left the EU in January.

It has focused on negotiating new trade pacts with countries around the world as its status-quo transition period ends on December 31. 

"How fitting it is to be in the land of the rising sun to welcome in the dawn of a new era of free trade," British Trade Secretary Liz Truss told reporters after the signing ceremony in Tokyo. 

"This is the first new free trade deal to be agreed since the UK once again became an independent trading nation," she added. 

The signing comes after Truss and Japanese Foreign Minister Toshimitsu Motegi reached a broad agreement in September. 

Motegi pointed out that the signing came about in just four and a half months since the start of negotiations. 

"This is a manifestation of the determination of Japan and the United Kingdom to carry on vigorously promoting free trade," the minister said. 

Britain has said the deal meant 99% of its exports to Japan would be tariff-free, and that it could increase trade by £15.2 billion in the long run, compared with 2018. 

The deal removes Britain's tariffs on Japanese cars in stages to zero in 2026, which is the same as in the Japan-EU trade agreement. 

Motegi said after the signing that he had agreed with Truss to work together so that the deal will come into force on January 1, 2021. 

He also said Japan welcomes Britain's interest in joining the 11-member Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) free trade deal, and intends to provide necessary support. 

Japan is already a member of the CPTPP, which also links Canada, Australia, Brunei, Chile, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam. 

In a meeting with Japanese Economy Minister Yasutoshi Nishimura, Truss said there would be a bigger opportunity with Britain's presidency of the G7 and Japan's chairmanship of the TPP-11 next year to challenge rising protectionism and make the case for free trade. 

Truss also expressed Britain's strong interests in joining the 11 member TPP trade pact, Nishimura said.

"If UK submits an application to join the TPP-11 next year, Japan will fulfil our role as a chair nation," he said.

Truss has already said Britain hoped to formally apply to join the CPTPP early next year.