WASHINGTON — Three American presidents have spent nearly 16 years alternately cajoling, coaxing, threatening and bombing Pakistan, all with a goal of trying to change the Pakistani government’s decisions about the factions it supports in Afghanistan’s desperate civil war.

The latest of those, President Trump, tried a different approach during his speech on Monday night. After chastising Pakistan for harboring militants and terrorists, he called on India — Pakistan’s archrival — to flex its economic influence in Afghanistan to help stabilize the country.

It was an unsubtle warning that Mr. Trump would not hesitate to put a thumb on one side of the balance in South Asian power politics, publicly drawing the United States closer to India while casting Pakistan as a friendless pariah state. But there was broad skepticism on Tuesday — both in Washington and Islamabad, the capital of Pakistan — that the tactic would force Pakistan’s government to abandon its longtime strategy in Afghanistan.

Some even predicted that Mr. Trump’s approach would have the opposite effect, causing Pakistani military and intelligence leaders to recommit to the groups they have long supported in the Afghan conflict. Some said it would further cement links between Pakistan and China, which sees India as a rival in Asia.