President Bush said Monday night he would order as many as 6,000 National Guard troops to secure the U.S. border with Mexico and urged Congress to give millions of illegal immigrants a chance at citizenship, as he tried to build support for a major overhaul of the nation’s tattered immigration laws.

“We do not yet have full control of the border and I am determined to change that,” the president said in pressing for his $1.9 billion plan in a 17-minute prime-time address from the Oval Office.

Bush gave strong support to a plan that would give many of the 12 million illegal immigrants in the United States an eventual path to possible citizenship – a move derided by some conservatives in his own Republican Party as amnesty. He rejected that term.

“It is neither wise nor realistic to round up millions of people, many with deep roots in the United States, and send them across the border,” he said. “There is a rational middle ground between granting an automatic path to citizenship for every illegal immigrant and a program of mass deportation.”

The Guard troops would mostly serve two-week stints before rotating out of the assignment, so keeping the force level at 6,000 over the course of a year could require up to 156,000 troops.

Still, Bush insisted, “The United States is not going to militarize the southern border.”

The White House wouldn’t say how much the deployments would cost, but said the troops would paid for as part of $1.9 billion being requested from Congress to supplement border enforcement this year.

The president timed his speech hours after the Senate began intense debate on an immigration bill that has been getting increasing attention in a year when all House seats and one-third of Senate seats are up for election. The rare televised, prime-time Oval Office address signified the high stakes for Bush, who has been asking for an immigration overhaul since his 2000 campaign.

House Majority Whip Roy Blunt, R-Mo., indicated Bush may have trouble getting some conservatives on board with his overall plan.

“While I appreciate the president’s willingness to tackle big problems, I have real concerns about moving forward with a guest worker program or a plan to address those currently in the United States illegally until we have adequately addressed our serious border security problems,” Blunt said.

Bush said the National Guard troops would fill in temporarily while the nation’s Border Patrol force is expanded. He asked Congress to add 6,000 Border Patrol agents by the end of his presidency and to add 6,700 beds so illegal immigrants can be detained while waiting for hearings to determine that they can be sent home.

For many years, the government has not had enough detention space to hold illegal immigrants, so they were released into society and most did not return for their court date. “This practice, called catch and release, is unacceptable and we will end it,” Bush said.

The Border Patrol would remain responsible for catching and detaining illegal immigrants, with National Guard troops providing intelligence gathering, surveillance and other administrative support. Yet the National Guard troops would still be armed and authorized to use force to protect themselves, said Bush homeland security adviser Fran Townsend.

They are to come from the four border states – California, Arizona, New Mexico and Texas – but those states’ governors may also seek Guard troops from other states.

The White House hopes deployments to the border will begin in early June.

Bush also called for enactment of a guest worker program to allow immigrants to take low-paying jobs, and he said employers must be held to account for hiring illegal immigrants. He said that a tamperproof identification card for workers would “leave employers with no excuse” for violating the law.