President Bush tonight will call for the deployment of National Guard troops to help secure the Southern border, as he seeks to build support within his own party for a guest worker program and coerce Congress to approve comprehensive immigration reform legislation this year.

The Senate resumes debate this afternoon on the immigration issue after lawmakers failed last month to reach agreement on it. Bush will use a prime time address from the Oval Office to outline his plan that includes deploying the Guard along the U.S.-Mexico border. A senior administration official tells CNN's Ed Henry that less than 10,000 troops would be pressed into service and they would act in a "supportive role" to existing border control agents. The Guard would not be apprehending immigrants illegally crossing the border, but would focus instead on conducting surveillance and building security infrastructure.

Early reaction to the Guard proposal has been mixed and it prompted Mexican President Vicente Fox to call Bush yesterday to express concern about a move to "militarize" the border. Bush reassured the Mexican president that he "considers Mexico an ally and a friend," according to a statement released by Fox's office following the conversation. White House spokeswoman Maria Tamburri said Bush told Fox the proposal being considered "is not a militarization of the border, but support of border patrol capabilities on a temporary basis by National Guard personnel."

"The President reiterated to President Fox his commitment to comprehensive immigration reform," Tamburri said.

Sen. Patrick Leahy (D-Vermont) is just one of many Democratic and Republican voices in Congress who argue the Guard is already overextended by its service in Iraq and the Gulf Coast.

"We're stretching them pretty thin now," Leahy said on CNN's 'Late Edition with Wolf Blitzer.' "We're going to make a border patrol out of them?"

But Senate Majority Leader Bill Frist (R-Tennessee) told Blitzer on the same program that such concern amounted to "whining" and "moaning."

"We've got to secure our borders, we hear it from the American people," he said. "We've got millions of people coming across that border -- first and foremost, secure the border whatever it takes. Everything else we've done has failed. We've got to face that. And so we need to bring in, I believe, the National Guard."

Stephen Hadley, Bush's national security advisor, noted that this is not a new idea and the Guard is already working along the border.

"This is something that's actually already being done," Hadley said on 'Late Edition with Wolf Blitzer.' "It's not about militarization of the border. It's about assisting the civilian border patrol in doing their job, providing intelligence, providing support, logistics support and training and these sorts of things."

In tonight's 8 p.m. ET speech, Hadley said Bush would "indicate where he stands and what he believes the way forward is on the issue of immigration." In addition to securing the border and promoting a guest worker program, the President will also talk about internal enforcement, Hadley said.

The President is gambling that his plan to police the border with U.S. troops will be enough to persuade conservative Republicans, mainly in the House, to accept his guest worker program. Many conservatives view this proposal as being too lenient on illegal immigrants. Frist predicted the Senate would approve a bipartisan bill by the end of the month.

"You're going to see the very best of the United States Senate as we have open amendment, open debate, take it to the floor, improve the bill that's on the floor, and we'll have it off before Memorial Day," he said.

But any legislation the Senate passes must then be reconciled with a House bill approved last year that does not include the guest worker program.

Tonight's speech will be Bush's 21st nationally televised prime-time address and a senior administration official tells CNN's Henry it's "crunch time" on getting a compromise on immigration reform.

Prior to his speech on immigration, Bush makes 12 p.m. ET remarks at the Annual Peace Officers' Memorial Service. He stays at the Capitol following his address and returns to the White House at 2:10 p.m. ET. Bush has no public schedule until his speech tonight.

First Lady Laura Bush marks today's deadline to sign up for the Medicare Prescription Drug Plan by attending an 11:05 a.m. ET enrollment event at the Shiloh Baptist Church in Washington. Sen. Edward Kennedy (D-Massachusetts) is scheduled to discuss the deadline in a 3 p.m. Senate floor speech. He sent out a biting news release yesterday accusing the administration of hurting "millions of seniors and disabled citizens" by failing to extend the deadline and urged Bush to support a Democratic bill to fix it.

"It's shameful that the new Medicare Drug Program did not put the interests of seniors first," he said. "I hope that the administration turns its attention to those seniors who will soon be facing huge gaps in their coverage called the 'doughnut hole' and support our legislation to fix it before it's too late."

Look to an 11 a.m. ET speech by Bush's top political advisor, Karl Rove, to see what he has to say on illegal immigration, the Medicare Prescription Drug Program and the midterm elections. The speech will take place at the American Enterprise Institute.

How well received was Sen. John McCain Saturday at his much hyped commencement speech to Liberty University graduates? The Arizona Senator didn't stick around for the reviews, as he was off to attend a Republican event in Salt Lake City. But the university's chancellor, Dr. Jerry Falwell described it in glowing terms. He said the reception McCain received was "indicative" that "if he continues on the track he's on, he could in fact co-opt the religious conservatives in the country the same way George Bush did, to help win the White House," CNN's Steve Brusk reports from Lynchburg, Virginia.

Arch enemies in the 2000 campaign, Falwell and McCain have since reconciled their differences and the influential Christian political activist has all but endorsed the Arizona Senator for the GOP's presidential nomination. But Falwell left the door open to supporting a handful of other Republicans in 2008 such as Sen. George Allen (R-Virginia), Sen. Rick Santorum (R-Pennsylvania) or Frist.

In fact, Falwell said he could back any candidate "as long as he or she espouses the same values that we espouse," and then he added for good measure, "Anybody but Hillary." Falwell is referring to Sen. Hillary Rodham Clinton (New York), who is the early favorite to win the Democratic presidential nomination.

And tonight perhaps we will learn more about the rift between Democratic National Committee Chairman Howard Dean and Democratic Congressional Committee Chairman Rahm Emanuel (Illinois) and Democratic Senatorial Campaign Committee Chairman Chuck Schumer (New York). Dean is scheduled to appear on 'The Daily Show with Jon Stewart.'