Afghan national security adviser Hamdullah Mohib told reporters Saturday that the government intended to participate in the conference in Istanbul, as well as another peace conference in Russia next week.

The United Nations is expected to broker the Istanbul conference but says it hasn’t yet received an invitation to do so.

While the format and purpose of the Russian event isn’t clear, the U.S.-proposed conference in Istanbul is aimed at replicating the format of the 2001 conference in Bonn, Germany, that installed Hamid Karzai as president following the ouster of the Taliban after the Sept. 11 attacks. The Taliban weren’t invited to attend it.

April’s conference will likely delay a full withdrawal of the remaining 2,500 American troops from Afghanistan beyond a May 1 deadline agreed between the Trump administration and the Taliban. Mr. Biden has said he wants to withdraw all U.S. forces from Afghanistan but possibly keep a residual force of counterterrorism troops.

The insurgents’ participation underscores the international consensus that for any peace arrangement to be successful, they must be involved in the political future of the country.

Peace talks between the Afghan government and the Taliban began in Doha, Qatar, in early 2020, but progress has been slow. U.S. officials hope a “second Bonn conference,” with high-level international observers, would pressure the two sides to work more rapidly to agree on a nationwide cease-fire and open up the prospect of negotiations for an interim government.

“This puts Biden’s fingerprints on whatever happens next. He’s clearly not dusting his hands and walking away,” a Western official who tracks the peace process said.

The Istanbul conference, though, risks deepening a rift between Washington and Kabul. President Ashraf Ghani has resisted the idea of an interim government, to the frustration of Western officials who see the president stepping aside as a necessary precursor for a broader peace agreement and cease-fire.

“The transfer of power through elections is a nonnegotiable principle for us,” Mr. Ghani said in a speech in parliament last week.

The Biden administration hasn’t said its official policy is to aim for an interim government, but in a recent leaked letter U.S. Secretary of State Antony Blinken urged Mr. Ghani to work with the Taliban to develop “a road map to a new, inclusive government.”

The announcement comes weeks before the Taliban traditionally launches its spring fighting season against government forces, which in the absence of progress in negotiations could spell renewed bloodshed. Alongside the diplomatic push, Western officials in Doha are working to get the two sides to commit to a significant reduction in violence. The Taliban have so far rejected a nationwide cease-fire, the No. 1 demand from the Afghan government.

A lot of uncertainty still surrounds the Istanbul conference, which among some Western diplomats is known as a “moon shot,” the Western official said, in which the U.S. is “aiming high and seeing where it lands.”

Write to Sune Engel Rasmussen at sune.rasmussen@wsj.com