Guatemala City (AFP) - Mexico has sent more than 100,000 Central American migrants back across its border with Guatemala since January, a 63 percent rise on the same period last year, the government announced Wednesday.

The hike in expulsions came as Washington increases pressure on its southern neighbor to curb illegal immigration from Central America, after tens of thousands of migrants flocked through Mexico to the US border earlier this year.

Mexico sent 54,037 Hondurans, 34,430 Guatemalans, 12,317 Salvadorans and 1,530 Nicaraguans by land to Guatemala, said Alejandra Mena, a spokeswoman for Guatemala's migration authorities.

Mexico tightened controls along its Guatemalan border after US President Donald Trump threatened to impose punitive tariffs on Mexican imports.

Meanwhile, expulsions of Guatemalans from the US increased by eight percent in the first eight months of the year, Mena said.

Around 1.5 million Guatemalans live in the US, of whom only about 400,000 are legal, according to official estimates. Remittances represented some $9.3 billion in 2018.

Mexico promised in June to take "unprecedented" steps to reduce the number of migrants reaching the US border.

The country is also urging international donors -- including the United States -- to fund a decade-long, $10-billion-a-year economic development package for the region in order to address the underlying problems driving migration.

The Mexican government has itself pledged $100 million for development programs in El Salvador, Guatemala and Honduras.

Guatemala in July signed a controversial pact with Washington which would oblige would-be asylum seekers traveling through the country to seek refuge there rather than the US.

The agreement has yet to be implemented because of legal challenges by NGOs on the grounds that Guatemala lacks the finances and security to cater for migrants.