As the federal government approaches another shutdown deadline, Montana's Democratic Sen. Jon Tester says there’s still work to be done on an immigration deal considered key to keeping things running.

Tester, who is working on a border security plan with a small group of lawmakers, said there is disagreement about what border security entails, with conservatives wanting “chain migration” included in the discussion.

“I look at border security as technology, manpower, wall, fencing however you want to put it," Tester said. "Some of the other folks are looking at it as those things plus chain migration and things that are more controversial. Chain migration is probably the big one.”

Chain migration is the term President Donald Trump uses to describe the practice of naturalized citizens and green card holders sponsoring the immigration of other family members to the United States. It is a common way for people to legally immigrate to the United States, with how-to instructions posted on the website of U.S. Citizenship and Immigration Services.

Tester said he thinks the Senate can get to a comprehensive immigration bill by May. For that, enough has to be done now to dissuade lawmakers who want immigration action from staging a protest vote like the one on Jan. 19, which led to a three-day government shutdown.

Tester did not vote to fund the government short-term, a decision he said was based not on immigration issues but on a lack of funding provided for Montana’s community health centers.

Immigration and border security have taken center stage as Senate Democrats aim to prevent the deportation of 1.8 million illegal immigrants who arrived in the United States as children and have lived most of their lives in the country. Those Democrats see leverage for their cause by no longer cooperating with Republican efforts to fund the federal government for only weeks at a time.

Congress is now four months overdue in passing an annual budget.

Trump has a few immigration issues he would like to add to the deal, namely chain migration and a $25 billion border wall along segments of the boundary between the United States and Mexico. Trump released his plans Thursday in a single-page paper.

The president wants to limit which family members an immigrant could sponsor into the country to only spouses and children. The argument is that immigrants are filling jobs that U.S. citizens might fill.

In addition, Trump proposed allowing 1.8 million illegal immigrants, who arrived in the U.S. as children, to stay. These are the immigrants now protected by the soon-to-expire Deferred Action for Childhood Arrivals, or DACA. DACA’s pending expiration was the reason many Democratic senators withheld votes Jan. 19; they aimed to keep the federal government funded for a few short weeks until a long-term budget could be passed.

Though Tester doesn’t believe chain migration should be part of a narrow border security deal, he is more agreeable to other Trump requests, including $25 billion for a wall between portions of the U.S.-Mexico border. Tester, however, does not support giving the money to the president all at once.

“I’m not going to give him a blank check. We’ve got three equal branches of government. We need to have accountability to make sure this money is being spent right,” Tester said. “You follow the money. If you give somebody $25 billion, accountability goes out the window.”

Tester said the Trump wall could win his support with more details, spreading the payments over 10 years, and giving the Senate regular chances to review the spending.

Asked about whether anyone still talks about holding Trump to his campaign rhetoric regarding Mexico paying for the wall, Tester said no.

“I haven’t heard that conversation here for nine months,” Tester said. “He was going to do it with trade there for a while and put some tariffs on, and the business community went crazy — which they should have, because it really would have had some negative impacts.”

In negotiations, Tester was asking that an additional 500 border and customs agents be hired annually until a current shortage of 3,600 officers is erased. He's asking that border agents use fiber optic detection technology to detect crossings.

Also, Tester is asking that agents be required to disclose when they're monitoring cell phone conversations. He wants grants offered to local law enforcement for border security work. 

The Senate was preparing to take a few days off beginning Wednesday to accommodate partisan political retreats. It wasn't likely that progress on border security would continue until everyone returned to work, Tester said.