Washington (CNN) President Donald Trump on Thursday claimed he would sign an executive order "next week" aimed at restricting US asylum rules, as he seeks to use a group of Central American migrants heading for the US border as part of his midterm election closing argument.

He also suggested that the US troops he dispatched to the US-Mexico border could fire on someone in the migrant caravan if the person threw rocks or stones at them.

In a meandering speech at the White House about immigration, Trump recycled many of the talking points he touts on the campaign trail -- but offered little in the way of concrete ways to address the problems he embellished.

Trump said his administration is finalizing an executive action that would limit asylum claims to legal ports of entry, claiming migrants frequently abuse the system by fabricating their need for asylum.

But he declined to specify how a change he described as a forthcoming executive order would work, or why he was convening a presidential address for a policy shift that is still in the preliminary stages.

Asked if he envisions US troops firing on anyone in the groups of migrants, Trump told reporters at the White House: "I hope not. I hope not -- but it's the military."

"I hope there won't be that," Trump said, but added that anybody throwing rocks or stones at the military service members will be considered to be using a firearm, "because there's not much difference when you get hit in the face with a rock."

Pentagon regulations only justify deadly force in face of threat

A US defense official told CNN that the troops deployed to the border will be operating under the standard rules on the use of force and will only use such force in self-defense.

Official Department of Defense regulations say "deadly force is justified only when there is a reasonable belief that the subject of such force poses an imminent threat of death or serious bodily harm to a person."

Lt. Col. Jamie Davis, a Pentagon spokesman, said following Trump's remarks that the Defense Department "will not discuss hypothetical situations or specific measures within our rules on the use of force, but our forces are trained professionals who always have the inherent right of self-defense."

"I would also emphasize that our forces are in support of DHS/CBP, who are performing law enforcement activities," Davis said.

Defense officials have repeatedly emphasized the troops at the border are there to support civil authorities and that they are not expected to come into any contact with migrants.

The top general overseeing US Northern Command said on Tuesday that "CBP (Customs and Border Protection) personnel are ... absolutely the primary and principal members that will be handling, specifically, the migrants."

"There could be incidental interaction between our military members and migrants or other personnel that might be in that area. And so we are making that our soldiers, our Marines are going to be fully trained in how to do that interaction," Gen. Terrence O'Shaughnessy said.

The general added, "They're going to understand the rules for that interaction, and they'll be consistent with CBP."

Remarks come ahead of midterms

Trump has focused increasingly on immigration heading into the final days of the midterms , as Republicans across the country struggle to match their opponents in drumming up voter enthusiasm.

Trump did not release details on the asylum proposal or how it would be implemented, saying only that he intended to sign an order sometime next week restricting asylum claims.

With three campaign rallies, a midterm election and a trip to France on the books, however, the President's schedule for next week is already crowded.

The President said he would sign an immigration-related executive order next week, but was not specific as to what it would address.

A White House aide had said earlier Thursday that Trump would unveil an executive action requiring migrants to request asylum at legal points of entry and preventing them from claiming asylum if they are caught crossing the border illegally. Although the President referenced such a policy in his speech, he offered no defense of how such a plan, once finalized, could be legal, given laws presently allowing migrants the right to claim asylum once they are on American soil.

The Trump administration has been looking at ways to limit the number of asylum seekers, with the President and his allies often describing asylum as a "loophole."

The Immigration and Nationality Act says that anyone who arrives in the US "whether or not at a designated port of arrival" may apply for asylum if he or she has a "well-founded fear of persecution on account of race, religion, nationality, membership in a particular social group or political opinion."

Earlier this year, Attorney General Jeff Sessions said victims of gang and domestic violence no longer qualify for asylum.

"Asylum was never meant to alleviate all problems, even all serious problems, that people face every day all over the world," he said in June.

As attorney general, Sessions has broad power over asylum procedures and the immigration courts, which are under the auspices of the Justice Department.

He has also suggested that those claims should be rejected even before asylum seekers appear before a judge and begin court proceedings and that the simple fact of crossing the border illegally could also be a factor in rejecting an asylum claim.

CNN reported earlier this week that the administration is also considering a plan to limit the number of migrants able to enter at legal ports of entry by "metering," essentially creating a waitlist to allow people to enter only if the Department of Homeland Security has the capacity to process and detain them at one of its facilities, a department official said.

In the past, the practice of metering has resulted in individuals deciding not to endure a lengthy wait to try to get into the country legally and instead to cross illegally. Should some of this group of migrants do the latter, they could face a tougher and higher standard for seeking asylum under the administration's plans.

White House aides had considered having Trump deliver an immigration speech earlier in the week, but the Pittsburgh synagogue massacre on Saturday delayed those plans.