ABC News' Jim Avila reports:

The U.S. border is as "secure as it's ever been," which is evidence enough that comprehensive immigration overhaul should start immediately, Homeland Security Secretary Janet Napolitano said today.

Separate commissions, or, as some Republicans have recommended, defined "triggers" are unnecessary, she said.

"Once people really look at the whole system and how it works, relying on one thing as a so-called trigger is not the way to go," Napolitano said at a breakfast hosted by the Christian Science Monitor.

Today at the press briefing, when White House Press Secretary Jay Carney was asked by ABC News whether the White House agrees with Napolitano's assessment, he said that there are a "variety of metrics" Democrats and Republicans use to measure progress on border security.

"We're working with Congress on this, with the Senate on this," Carney said. "Progress has been made…He [Obama] has demonstrated his seriousness on this issue and - as has Secretary Napolitano. But it is something that we're - you know, is not a done project. We have to continue working on it."

When it comes to the line Napolitano said this morning "getting in the back of the line" is "easier said than done" when the line is constantly fluctuating.

Some Republicans have suggested that before any "pathway to citizenship" for undocumented immigrants can begin, the federal government must prove the border is secure with hard numbers that would convince a new commission or congressional committee.

"Border security is not somehow different than looking at the overall immigration system. They go together," Napolitano said. "We know the key driver, a key driver, is the demand for labor."

The secretary added that the United States needs to make legal immigration easier because the slow process provides a real incentive to cross illegally.

"If you are going to be separated from your family for 10 years, and that happens way too often, 0r if you can't get the right kind of visa for 15 years," she said. "If you want to take pressure off the border, you actually have to look at the immigration system as a whole."

Napolitano repeated her contention today that fewer undocumented immigrants are crossing the border illegally than ever before and there is no way to improve those numbers without immigration overhaul.

"We need a national e-verify or national system, so employers have a way to comply with immigration law," she said. "We need a better way for people to come legally through ports."

But she conceded that the 11 million undocumented immigrants will need to pay a fine and "get right with the law, they did break the law."

The secretary says she is optimistic an immigration bill will emerge from Congress because "I'm always optimistic."

On other issues, Napolitano defended the Transportation Security Administration's decision to allow small knives on a plane.

She said it's their job to prevent bombs from exploding on planes.

"You are talking about a small knife; there are already things on a plane that somebody could convert into a small sharp object" and knives are no threat to an entire plane, she said.

"So from a security standpoint, it's the right decision," she added.

As with her concession that the announcement to release 3,000 undocumented detainees from Immigration and Customs Enforcement came as a surprise, Napolitano said the knife-policy announcement "could have [been] done better."

"A little more legislative and public outreach before we announced the decision; tried to give it a softer landing, as it were," she said.

Finally, a bit of Napolitano trivia: She doesn't email because "it sucks up time." And the former Arizona governor has no plans to run for president, but did not issue a blanket denial.

"That kind of contemplation is the type of thing that will keep me up at night," she said, "and I lose enough sleep as it is."

Story Updated at 2:04 p.m.