Foreign Secretary Boris Johnson, who is in The Gambia, has said he is "very pleased" the West African state intends to rejoin the Commonwealth.
His visit, the first to The Gambia by a British foreign secretary, comes weeks after long-time ruler Yahya Jammeh went into exile after losing elections.
Mr Jammeh took The Gambia out of the Commonwealth in 2013, calling it a neo-colonial institution.
New President Adama Barrow had promised a return to the 52-nation grouping.
Before leaving for Banjul, Mr Johnson said: "We will ensure this happens in the coming months.
"The strength of our partnerships show that Global Britain is growing in influence and activity around the world."
The Commonwealth secretariat said it welcomed the news, saying the formal process of rejoining would have to be agreed by the 52 heads of government.
"When The Gambia left the Commonwealth in 2013, the heads of government... noted its decision with regret. We looked forward to the country's eventual return because it was part of our very close knit family and our doors have always remained open," a spokesman said.
Last week, the European Union promised The Gambia an aid package of nearly £65m ($81m) - almost three years after freezing its assistance to the West African nation.
Mr Barrow, who was sworn in last month, has also said The Gambia will reverse its move to withdraw from the International Criminal Court (ICC).
In a statement on Monday, the government said it had written to UN chief Antonio Guterres to inform him of its decision "to discontinue the withdrawal notice".
A former Gambian information minister had referred to the court last year as "an International Caucasian Court for the persecution and humiliation of people of colour, especially Africans".
The move is a blow to Africa's anti-ICC lobby - which includes South Africa, Namibia and Burundi.
At the annual African Union summit held this month, leaders called for a mass walk-out from the ICC, but faced opposition from other countries, including Nigeria, Senegal and The Gambia.
'Return from 22 years in exile'
The Foreign Office said as well as holding talks with Mr Barrow, Mr Johnson would visit the UK-funded Medical Research Council and speak to Chevening scholars and workers and employers in the tourism industry.
The West African state is a popular holiday destination for Britons. Thousands had to be evacuated last month because of security concerns when Mr Jammeh was refusing to hand over power after losing December's elections.
Mr Barrow, whose swearing-in was held in neighbouring Senegal, is to be inaugurated as president in a ceremony at the national stadium on Saturday.
Several heads of state are expected to attend. Local dignitaries may include former Vice-President Alhagie Saihou Sabally, who local media said had returned to the country on Monday after 22 years in exile.
Mr Jammeh, who took power in coup in 1994, is now in exile in Equatorial Guinea after West African leaders deployed troops to The Gambia to ensure he left power.
Mr Johnson will go on to Ghana for talks with President Nana Akufo-Addo on Wednesday.
Referring to him and Mr Barrow, Mr Johnson said: "Their elections highlight the continuing strengthening of democracy in West Africa."