Mexican officials are carrying out the Donald Trump administration’s immigration agenda across widespread stretches of the border, undercutting the Mexican government’s promises to defend migrants and support their search for a better life.

The Mexican authorities are blocking groups of migrants at border towns, refusing to allow them onto international bridges to apply for asylum in the US, intercepting unaccompanied minors before they can reach American soil, and helping to manage lists of asylum seekers on behalf of the American authorities to limit the number of people crossing the border.

Breaking with decades of asylum practice, the Mexican government has also allowed the Trump administration to send more than 120 men, women and children to Tijuana while they await decisions on their asylum applications in the US. The programme could be expanded to other border crossings as soon as next week.

Officials inside the administration of Mexico’s new President, Andrés Manuel López Obrador, have called his stance on migrants a strategic decision not to anger Trump.

He doesn’t believe he can change Trump’s mind, they contend. Furthermore, the officials say, López Obrador has not wanted to jeopardise other aspects of the deeply interconnected relationship between the two countries, ranging from elaborate regional trading arrangements to information-sharing on border security, transnational crime and terrorism. So he has avoided a bruising and potentially costly public fight over the issue.

A lifelong defender of the poor, López Obrador often refers to his plans for Mexico as a grand transformation.

But not everything has transformed.

Exhibit A is the Migrant Protection Protocols, the Trump administration’s policy to require asylum seekers to remain on the Mexican side of the border while they await decisions on their fate. Rights groups contend that it dumps migrants in an increasingly violent Mexico and impairs their access to legal counsel and family support in the US.

López Obrador’s administration, which came into office saying it would not cooperate with Trump’s anti-immigration agenda, has gone along with it on several fronts, including accepting women and children despite earlier promises to take only adult male asylum seekers.

The Mexican government argued the policy requiring asylum seekers to wait in Mexico was imposed on them by the US and they consented for humanitarian reasons.

It is also true that for López Obrador, giving in to some of Trump’s border demands and rarely saying a word against the American President in his daily media briefings carries little political cost at home.

To many Mexicans, the fate of migrants is secondary to domestic concerns about jobs, security and corruption. López Obrador retains an 80 per cent approval rating, despite his government’s willingness to take back migrants applying for asylum in the US.