After years of advocating peace talks as the only way out of the Afghan war, President Hamid Karzai will soon need to decide whether he is willing to participate in an emerging diplomatic process that his top advisers claim has left him marginalized by both the United States and the Taliban.

Although Karzai agreed this month to bless the opening of a Taliban diplomatic office in Qatar, his administration has become increasingly frustrated by talks between U.S. officials and the insurgency, leaving top Afghan government officials unsure where they fit in the negotiations.

The Obama administration, eager for a political settlement to the decade-long war, saw Karzai’s acquiescence to the Qatar office as a signal that his government is on board with a process that had been stagnant for years but has lurched to life in recent weeks.

In interviews, however, Afghan officials say they feel sidelined and misled, left guessing at the character of the negotiations, even as U.S. officials emphasize the importance of “Afghan-led” talks.

“If we continue this way, we’re doomed,” said Shaida M. Abdali, Karzai’s deputy national security adviser.

Marc Grossman, the U.S. special envoy to Afghanistan and Pakistan, will visit Kabul on Saturday for what Afghan officials say will be a pivotal point in negotiations. The officials say they will demand increased clarity from the U.S. diplomat, and a promise that the peace process will promptly become Afghan-led.

The United States insists that it has kept Karzai briefed throughout the nascent peace process, and that early contacts with Taliban representatives were intended only to build confidence before real negotiations begin between the Afghan government and the insurgency. U.S. officials also claim that they have slowed the process at Karzai’s request, and that there have been no direct contacts with the Taliban since October.

But senior Afghan officials, who agreed in principle to early talks between U.S. envoys and the Taliban, say American diplomats have overplayed their hand, making tentative concessions that Karzai opposes and creating distrust that could cripple the peace effort.

The Afghan government is now operating from a position of “deep suspicion,” according to one senior Karzai adviser. The suspicion stems from both the substance of early talks between the United States and the Taliban, and disappointment that after more than a year of quiet negotiations, Karzai is still not playing a lead role, said the adviser, who spoke on the condition of anonymity to discuss a sensitive issue.

Late last year, the United States had prepared to transfer Taliban prisoners who are now being held at the U.S. detention facility in Guantanamo Bay to Qatar, where they would be held under house arrest. In return, the Taliban would publicly repudiate international terrorism. But Karzai blocked the deal, insisting that if the prisoners were to be released, they should be handed over to the Afghan government, U.S. officials have said.

“That is our constitutional right,” Abdali said. “We are a legitimate government, and we should be treated as one.”

Any transfer of Taliban prisoners from Guantanamo would require the administration to certify to Congress that they would not escape and pose no threat to U.S. security, conditions that would be difficult to meet in Afghanistan’s prison system.

For Afghan officials, that early disagreement over the prisoners cast doubt on the American role in peace negotiations, raising concern that U.S. compromises might weaken Karzai’s position before the Afghan government could take charge of negotiations.

The complaints from Karzai’s inner circle could frustrate U.S. officials, who had assumed they had arrived at a basic agreement with Karzai on the strategy for negotiations. But even the setting for talks — considered by Western diplomats to be critical groundwork for the peace process — remains a point of contention in Kabul.

“We’re fine with a diplomatic office in Qatar, but we still want negotiations to take place in Saudi Arabia or Turkey,” said Aymal Faizi, Karzai’s spokesman.

Some Western officials attribute the recent expressions of doubt by Afghan officials to Karzai’s anxiety over reconciling with the Taliban, an idea that still faces widespread opposition in Afghanistan.

U.S. officials began meeting with Mohammed Tayeb al-Agha, an aide to Taliban leader Mohammad Omar, in November 2010. Karzai’s advisers say their frustration has accumulated since then, as they have waited to take on a more significant role. The September assassination of Afghan peace council chief Burhanuddin Rabbani by a man posing as a Taliban envoy only exacerbated that tension.

In the absence of direct talks with Taliban representatives in Qatar, Karzai has relied on his own set of contacts within the organization. But his advisers say those conversations are no substitute for the kinds of talks the United States has held with men who have apparently been selected by the Taliban’s leadership to serve as the organization’s negotiators.

In the absence of clear information from U.S. officials, top Karzai advisers said they have grown worried about rumors that the United States has offered the Taliban seven provinces in southern Afghanistan. U.S. officials flatly deny such a proposal exists.

Karzai’s advisers say their anxiety could be dispelled during Grossman’s visit on Saturday.

“We need to know exactly what they’ve said to the Taliban and what they’ve heard in return,” one Afghan official said. “We need to be involved in the future of our own country.”

Although Afghan officials have mostly directed their frustration toward the U.S. role in negotiations, the Taliban poses a potentially larger hurdle to the peace process. In the group’s statement this month about its willingness to negotiate, it acknowledged the United States as a negotiating partner, but not Karzai’s government.

Even though the Taliban has never formally agreed to direct talks with the Afghan government, the Karzai administration remains insistent that it could promptly begin productive talks with the insurgency if the United States were to cooperate.

On the U.S. side, some are less hopeful about the Taliban’s willingness to engage with Karzai, claiming the group prefers to talk to the United States. The Taliban is “not willing to sit down with the Afghan government,’” one U.S. official recently said. “Our job is to see if we can break through that door.”

Staff writer Karen DeYoung contributed to this report from Washington.