By Krittivas Mukherjee

NEW DELHI, Feb 2 (Reuters) - An initiative by Western powers seeking peace with the Taliban in Afghanistan is forcing India to modify its policy toward the hardline Islamists to avoid being marginalised in a country Delhi sees as key to the country's security.

Officials fear an Afghan plan endorsed by global powers to win over Taliban foot soldiers will give rival Pakistan a greater say in the peace process and may ultimately lead to a Taliban takeover once Western forces leave Afghanistan.

The six-decade India and Pakistan rivalry since their independence from Britain in 1947 has turned Afghanistan into a proxy battleground, whose control both countries see as vital to their interests.

Their rivalry complicates Western efforts to stabilise Afghanistan.

Afghan President Hamid Karzai's call on Saudi Arabia and Pakistan to help reach out to the Taliban is threatening to undo eight years of financial and diplomatic investment that gave New Delhi great influence over Kabul.

"Delhi's failure to respond to the changing situation in Afghanistan might cause huge setbacks for India," C. Raja Mohan, a foreign policy expert at the U.S. Library of Congress, wrote in the Indian Express newspaper on Monday.

"India had a great run in Afghanistan in Phase One (since 2001 until recently) ... However, the stasis that had gripped India's security policy in recent months and some fine manoeuvring by the Pakistani army threaten to marginalise Delhi in Phase Two."

The urgency to acquire a role in Afghanistan, even if limited, may have already prompted India to soften its stand on the Taliban so as not to be seen as blocking the peace process.