A U.S. special envoy has departed Friday for a trip aimed at bringing the Afghan government and the Taliban to the negotiation table, the U.S. State Department said Saturday.

U.S. Special Representative for Afghanistan Reconciliation Zalmay Khalilzad is scheduled to travel to Doha, Islamabad, Kabul, Oslo and Sofia, the State Department said in a statement.

"In Doha and Kabul, Ambassador Khalilzad will press for resolution of the remaining issues ahead of intra-Afghan negotiations, specifically final prisoner exchanges and reduced violence," said the statement.

During his five-stop trip, the diplomat will also seek Pakistani support to advance the intra-Afghan negotiations and inform the United States' North Atlantic Treaty Organization (NATO) allies of the Afghan peace process.

"The parties are closer than ever to the start of Intra-Afghan Negotiations, the key next step to ending Afghanistan’s 40-year long war," read the statement.

Khalilzad's trip came at a time when the process of prisoner exchanges between the Afghan government and the Taliban has reached an impasse and the country has seen growing violence recently.

Under the Taliban-U.S. agreement signed on Feb. 29, the Afghan government would release 5,000 Taliban prisoners and the Taliban would free 1,000 prisoners of the government.

However, the slow pace of the release of prisoners has delayed the intra-Afghan dialogue, which was scheduled to start on March 10.

Moreover, in early July, the Afghan government reportedly suspended the release of the last batch of Taliban inmates over their involvement in serious crimes, which had widened the two side's split.

"The Afghan government once again stated its firm stance of not releasing nearly 600 Taliban prisoners who are reportedly guilty of serious crimes beyond membership in the Taliban," local Tolo News TV reported on July 7.

Taliban's Doha office spokesman Suhail Shaheen tweeted on Thursday that the Taliban is "likely" ready to begin intra-Afghan negotiations immediately after the Muslim holiday of Eid al-Adha at the end of July in case the prisoner exchange is completed.

Shaheen also accused the government of recapturing previously released Taliban prisoners, who, he said, had adhered to the government's instructions to stay at home and not return to the battlefields.

However, the Afghan government refuted the accusation, saying a number of released prisoners have in fact returned to the battlefields.

One of Khalilzad's main tasks is to press for a deal between the two sides on this tricky problem, which serves as a precondition for starting the peace talks.

"Although significant progress has been made on prisoner exchanges, the issue requires additional effort to fully resolve," the State Department said in its statement.

The soaring violence across the country and the intensified attacks from both sides have complicated the situation.

Two Afghan national security force members and 45 Taliban militants were killed during separate clashes on Friday night.

On Wednesday, government warplanes killed dozens of Taliban militants in Adraskan district of the western province of Herat.

However, the Taliban and some locals have disputed the claim, saying the majority of the killed were civilians.