(Reuters) - Grappling with a ballooning number of migrants at the U.S. southern border, President Donald Trump has suggested increasingly bold steps to fulfill his signature campaign pledge to stem illegal immigration.

Central American migrants walk during their journey towards the United States, in Villa Comaltitlan, Mexico April 18, 2019. REUTERS/Jose Cabezas

Yet many of his administration’s ideas have been hindered by legal, practical and political obstacles.

Meanwhile, the flow of migrants seeking asylum or a better life in the United States continues to swell. By March, the number of illegal entrants into the country had surged to the highest level in more than a decade.

On Wednesday, the acting director of the U.S. Department of Homeland Security Kevin McAleenan visited the Texas border to underscore the administration’s concerns about a growing crisis.

The U.S. Customs and Border Protection confirmed Thursday that the agency would set up two temporary tent facilities in Texas to process migrants, each with a capacity to hold up to 500 people. Such camps have been criticized by Congress members for holding migrants too long and not providing adequate places to sleep or shower.

The president, whose statements and tweets suggest a rising level of frustration, recently cleaned house at the Department of Homeland Security, firing Secretary Kirstjen Nielsen and several other high-ranking staff. He has vowed to move in a “tougher direction.”

But a look at several significant Trump Administration ideas or policies shows the difficulty the president faces in trying to reverse the tide of migration, which today is largely driven by poverty, corruption, crime and other factors in Central America.

Some examples of administration proposals or policies that have run, or may run, into trouble:

DETAIN ASYLUM SEEKERS INDEFINITELY

U.S. Attorney General William Barr on Tuesday issued a ruling that allows asylum seekers who cross the border illegally to be held without bond as they challenge their deportation – a decision affecting perhaps tens of thousands of migrants. It was the latest move by top justice officials seeking to reshape legal precedent in the country’s U.S. immigration courts.

(See graphic here on such actions: tmsnrt.rs/2XmGDDg)

Rights groups have already threatened to sue over the measure - which goes into effect in 90 days - and as a practical matter, additional detention space would be needed, requiring funding from Congress. Until that happens, many migrants are likely to continue to be released with an order to appear in court.

SEND IMMIGRANTS TO SANCTUARY CITIES

Earlier this month, Trump proposed sending “an unlimited supply” of immigrants who are fighting deportation to so-called sanctuaries - the hundreds of cities, counties and states where law enforcement limits its cooperation with Trump’s crackdown on immigrants living in the country illegally.

Immigration experts said it would be costly to transport migrants from the border and would require shifting funds from Border Patrol and other operations. In addition, the migrants would be free to move elsewhere once released.

CLOSE THE BORDER WITH MEXICO

The administration recently backed off a threat to shut the southern border, one of the busiest in the world, amid opposition from Democrats as well as often Republican-friendly business groups. The U.S. Chamber of Commerce, called the idea an “economic calamity.”

MAKE ASYLUM SEEKERS WAIT IN MEXICO

One of the boldest proposals by the Trump administration has been to tap a little used clause in immigration law to send hundreds of migrants who ask for asylum in the United States back to border towns in Mexico to wait months - or potentially years - for their cases to be resolved in U.S. courts.

Local Mexican officials say their towns are already overwhelmed with migrants who have nowhere to live and few job prospects, while immigration advocates say those who are stuck in Mexico often have trouble finding lawyers and receiving proper notice for their U.S. hearings. A federal judge ordered a halt to the policy but an appeals court said it could continue while the administration appeals.

DETAIN MIGRANT CHILDREN

The current wave of migrants includes many more families, as opposed to the single men who flocked north in the past. That has caused the administration to take another look at a 1997 agreement, known as the Flores settlement, that strictly limits detention of children.

The administration has said repeatedly that t wants to scrap the legal deal and propose new regulations. It is unclear where - and with what funding - the government would detain the youngsters. Legal challenges to this proposal have been in the works from the moment it was announced.