Credible intelligence from multiple sources indicates that Usama bin Laden's Al Qaeda (search) terror network plans to attempt an attack on the United States "within the next few months."

"Disturbing intelligence indicates Al Qaeda's specific intention to hit the United States hard," Attorney General John Ashcroft (search) said Wednesday in a press briefing at the Justice Department.

Ashcroft and FBI Director Robert Mueller (search) said federal officials were on the lookout for seven people — six men and one woman — who they believe are connected to the terror plans.

"They all pose a clear and present danger to America — they all should be considered armed and dangerous," Ashcroft said.

"For the next few months, we have reason to believe there will be a heightened threat to United States' interest around the world," said Mueller, who stressed that because no firm details are known about such an attack, it's imperative to find the seven individuals.

But, "we do not have specific information about the origin of a specific terrorist plan," Ashcroft added. Although "I think it's fair to say this is intelligence that's come in over time. This isn't a one shot or other thing."

U.S. intelligence officials received "several" credible reports that terrorist groups like Al Qaeda may be planning an attack during one of the major events scheduled for this summer, Homeland Security Secretary Tom Ridge (search) said earlier Wednesday.

Ridge told Fox News a "couple" of the reports were "deemed credible that Al Qaeda would like to attack." And he said the threat "is one we take very seriously."

The FBI plans to dispatch a bulletin to some 18,000 state and local law enforcement agencies warning of the threat.

'Fighting Terrorists Is a Tough Business'

Public statements made by Al Qaeda suggest "that it's almost ready to attack the United States," Ashcroft said.

Just after New Year's Eve, for example, the terrorist organization announced that plans for an attack within the United States were 70 percent complete; after the March 11 Madrid train bombings, a spokesman for the group said 80 percent of arrangements were complete.

"The Madrid railway bombings were perceived by Usama bin Laden and Al Qaeda to have advanced their cause," Ashcroft said, referring to the change in government that took place when elections were held several days after the attacks. He added that Al Qaeda and bin Laden likely hope such an attack on U.S. soil "would lead to similar consequences."

Mueller and Ashcroft encouraged the public to report any suspicious activity to proper authorities and said the American public is able to thwart an attack by being on the lookout.

"For 32 months now, we haven't had a major terrorist attack on American soil," Ashcroft said. "We are winning the war on terror but we should never forget that it is a war. Fighting terrorists is a tough business. I have faith Americans will continue to be equal to the task."

Officials said it's possible Al Qaeda will try to infiltrate young Middle Eastern extremists into America, as they did before Sept. 11, 2001. Intelligence also confirms that the network is seeking recruits who can portray themselves as Europeans.

"Al Qaeda is a resilient and adaptable organization known for altering tactics," Ashcroft said.

A think tank study revealed this week that more than 18,000 potential terrorists in its global network and a swelling membership thanks to the war in Iraq.

The intelligence does not include a time, place or method of attack but is among the most disturbing received by the government since the Al Qaeda attacks of Sept. 11, 2001, a senior counterterrorism official said.

"There is clearly a steady drumbeat of information that they are going to attack and hit us hard," said another senior federal counterterrorism official.

There was no immediate plan to raise the nation's terror threat level. Asa Hutchinson, Homeland Security Department undersecretary for border and transportation security, said, "We don't have the specific information that would justify raising it or would cause us to do it."

"Every single day, we operate as if there are terrorists within the United States … we cannot forget that we are an open and diverse and welcoming country," Ridge said, adding that 5 million to 6 million people cross into the United States every year.

"It would be foolish to think there may not be terrorist cells that already exist within the United States … On a day to day basis, it's our job to be smarter and to use our people and technology to increase security around the country," Ridge continued. "We don't need to raise the threat level to do that. That's our job 24-7."

Dealing With the Threat

The FBI has already created a special task force to deal with the summer's threat. The task force is intended to ensure that no valuable bits of information or intelligence fall through the cracks — as happened repeatedly before the Sept. 11 attacks.

Other actions to be taken include new FBI interviews with people who may have provided valuable information in the past and a fresh examination of older investigative leads to determine if they might point to elements of the summer plot.

The FBI will be working with law enforcement partners and the Joint Terrorism Task Forces to assess intercepted information.

"We will be reviewing every lead we've had for the past year to see if taken in today's light it means something different," one counterterrorism official said.

Some Democrats charged that the administration was needlessly scaring people, perhaps to divert attention from the continuing problems in Iraq. Ashcroft's announcement came two days after President Bush began a monthlong initiative to explain administration policy on Iraq and the war on terrorism.

Massachusetts Sen. John Kerry, the presumptive Democratic presidential nominee, used the announcement to take a slap at the administration and its homeland security efforts.

"Every administration official since Sept. 11 has said to us that it is not a question of if — it is a question of when," Kerry said in a statement, before then questioning Bush's decision to cut programs like Community Oriented Policing Services, and asking why there still isn't 100 percent inspection of containers at the nation's ports and chemical and nuclear plants.

"We deserve a president of the United States who doesn't make homeland security a photo opportunity and the rhetoric of a campaign," Kerry said. "We deserve a president who makes America safer."

Summer Packed With High-Profile Events

Beginning with Saturday's dedication of the new World War II Memorial in Washington, the summer's high-profile targets in the United States include the G-8 summit in Georgia next month, the Democratic National Convention in July in Boston and the Republican National Convention in August in New York.

"I think people in both cities have to recognize that by hosting a symbol of democracy, they become a target in some respects but … we have to make sure the political process goes on," Massachusetts Gov. Mitt Romney, a Republican, told Fox News.

There also is concern terrorists might try to mount an attack to coincide with the November election.

"Unfortunately, the same events that fill most of us with hope and pride are seen by terrorists as opportunities for terrorist attacks," Mueller said.

Officials also are concerned about so-called soft targets such as shopping malls anywhere in the United States.

"Ultimately, the most effective weapon against terrorism is intelligence work" through methods such as those allowed under the USA Patriot Act (search), Romney said. "That's really the way to protect against an attack. You really can't protect everything with policemen."

Special security attention already is being focused to the nation's rail, subway and bus lines. The FBI last week sent out an intelligence bulletin to law enforcement agencies urging vigilance against homicide bombers.

Some 2,300 Immigration and Customs Enforcement agents are being deployed to prevent terrorists from coming in through the borders and to assist in security for the high-profile events as many as 20 agents each day working with the Secret Service to protect the campaigns of President Bush and Kerry.

Fox News' Catherine Herridge, Liza Porteus, James Rosen, Anna Stolley and The Associated Press contributed to this report.