* Offensives unlikely to have impact on Afghan fight now
* Pakistan has thinned defensive lines on Indian frontier
WASHINGTON, April 28 (Reuters) - Pakistan has shifted more than 100,000 of its troops from its Indian frontier to spearhead an unprecedented crackdown on militants along the Afghan border, but the shift is unlikely to have an immediate impact on fighting in Afghanistan, the Pentagon said.
In a report to Congress released on Wednesday, the Pentagon estimated that between 130,000 and 150,000 Pakistani troops were taking part in offensives against militants in the semi-autonomous tribal regions, known as the Federally Administered Tribal Areas, or FATA, and the Northwest Frontier Province, near Afghanistan.
The Pentagon said that represented the biggest deployment of Pakistani military forces on the western border in the country’s history. To carry it out, Pakistan has shifted more than 100,000 troops from the eastern border with India, according to the report.
"This unprecedented deployment and thinning of the lines against India indicates that Islamabad has acknowledged its domestic insurgent threat," the Pentagon said.
The Pentagon issued the report one day before the prime ministers of India and Pakistan are due to hold their first meeting in nine months. Washington has sought to improve frayed ties between the South Asian rivals, who have fought three wars since their independence from Britain in 1947.
In the report, the Pentagon said Pakistani military operations in the FATA and the Waziristans have had an impact across the border, placing a "high degree of pressure on enemy forces and reduced insurgent safe haven" in eastern Afghanistan.
But the Pentagon played down the immediate impact of the Pakistani crackdown on the strength of the broader Taliban-led insurgency against U.S. forces in Afghanistan, saying Islamabad’s crackdown had thus far "focused almost exclusively on internal threats."
"While this evolving approach is unlikely to have significant impact on the Afghan insurgency in the short term, it offers opportunities in coming months to have a greater impact on the conflict in Afghanistan depending on how PAKMIL (Pakistani military) operations evolve," the report said. (Reporting by Adam Entous and Phil Stewart; Editing by Peter Cooney)