The United States is sending up to 2,000 more marines to Afghanistan to step up the hunt for Osama Bin Laden and other al-Qaeda and Taleban leaders.
The Pentagon says the deployment has been planned for some time
The troops will join about 12,000 US troops already in the country.
Pakistan has also announced it is reinforcing its operation in the tribal areas on its side of the border.
Pakistani forces there have launched a full-scale assault against al-Qaeda and foreign militants and the tribesmen believed to be protecting them.
"We are pursuing with the Pakistanis parallel, complementary efforts on both sides of the borders," a US military spokesman told the BBC.
This amounts to a significant stepping up of the pressure, but is not the final US push against al-Qaeda - nor an explicit mission to capture Bin Laden, says the BBC's defence correspondent Jonathan Marcus.
The US launched a new offensive in Afghanistan two weeks ago.
Operation Mountain Storm - like many earlier operations - was intended to find and destroy remaining al-Qaeda and Taleban elements.
Before the launch, the Pentagon had despatched key reinforcements to Afghanistan including special forces and a variety of airborne surveillance systems.
US military spokesman in Kabul, Colonel Brian Hilferty, told the BBC the new deployments - currently based on ships in the Persian Gulf - would join the hunt "both for the leadership of the Taleban - and al-Qaeda".
"We are getting much better intelligence from the Afghan people" on the whereabouts of the militants, Col Hilferty told the BBC's Newshour programme.
There was a lot of talk just a few weeks ago about a major US "spring offensive" designed to knock out any chance of the Taleban and al-Qaeda re-grouping, our correspondent says.
And even though this might not be the "spring offensive", this is a major operation that fits into a continuous pattern, he says.
Afghanistan is also preparing for critical elections and Operation Mountain Storm along with the additional marines are all part of a package intended to enable those elections to take place in an atmosphere of relative calm, our correspondent says.
Pakistan's information minister said more army troops were being mobilised for what might be another onslaught against the al-Qaeda and foreign militants in the mountainous region of South Waziristan province.
The announcement follows the failure of efforts by tribal leaders to negotiate the release of 14 hostages, most of them government forces taken at the beginning of the offensive last week.
In an interview with a leading Pakistani newspaper, the army commander in charge of the operation, General Saftar Hussein, said he wanted to wind it up by Saturday.
He said the mission to destroy hundreds of militants and deny them sanctuary had been accomplished.
About 30 soldiers and a number of militants have died in the fighting.
The government launched the operation - involving 5,000-7,500 troops - believing a "high-value target" was among the militants.
That figure was initially reported to be al-Qaeda deputy leader Ayman al-Zawahri, but the BBC's Paul Anderson in Islamabad says that if he was there it appears he has now escaped.