A Soviet promise to withdraw several thousand troops from Afghanistan this year did not appear here today to have raised Pakistan's limited hopes for this week's round of Geneva negotiations on the 6 1/2-year-old Afghan war.

In recent weeks, Pakistani officials have stressed the wide differences that emerged in the last round of talks on a timetable for a complete Soviet troop withdrawal. One official suggested that the May round of talks may have revealed what he called "a conceptual gap" between the Afghan and Pakistani negotiators, who are to resume their indirect talks Thursday in Geneva.

After Soviet leader Mikhail Gorbachev announced yesterday that the Soviets would withdraw six regiments from Afghanistan this year, a Pakistani Foreign Ministry spokesman said simply that it was a "welcome decision" and that Pakistan hoped it would "be a small step toward the complete withdrawal of the Soviet forces in Afghanistan."

Gorbachev said the decision was meant to "speed up political settlement" in Afghanistan. However, Pakistan offered no suggestion that it had raised hopes -- which Pakistani officials and political analysts have characterized as limited -- for the new round.

Pakistan and the Soviet-backed Afghan government have been negotiating for more than four years on a plan to remove Soviet troops from Afghanistan while ending Pakistan's support for the Afghan resistance movement fighting the Soviets and the Afghan government. At Pakistan's insistence, the talks are indirect, with United Nations Undersecretary General Diego Cordovez shuttling between the two delegations as mediator.

The seventh round in May was the first to take up the central issue of a timetable for a Soviet withdrawal. The session was suspended, however, after the Afghans reportedly offered a four-year schedule and the Pakistanis suggested four months.

Since the May talks, Pakistani officials have questioned whether the Soviet Union was negotiating seriously. Foreign Secretary Abdul Sattar said this month that the Afghan proposal "caused great disappointment" and would have to be replaced by a "reasonable, acceptable and short" time frame of "months, not years," if the talks were to progress.

Also, this month, the Pakistani Foreign Ministry said increased artillery and air violations of Pakistan from Afghanistan were harming the climate for a politcial solution. Pakistani and foreign analysts say the border incursions and a wave of sabotage attacks in western Pakistan are part of a Soviet and Afghan campaign to pressure Islamabad into softening its support for the Afghan resistance, or mujaheddin.

Last weekend, three land-mine explosions in Pakistan's Kurram district reportedly killed six Afghan refugees and wounded seven others. Police in the northwestern city of Peshawar said they had arrested two agents of the Afghan secret police, KHAD, confiscating land mines and explosives from them.

Pakistani newspapers also reported three incidents of artillery or mortar shelling from Afghanistan during the past five days -- two of them at Chaman, a major border village 60 miles northwest of here.

Pakistani officials have stressed privately their view that the troop withdrawal schedule should reflect the time logistically necessary for a pullout. By pressing for a slow and prolonged withdrawal following a Pakistani cutoff of aid to the rebels, they argue, the Soviets are hoping to be able to crush the resistance and cement the shaky Afghan regime in place before finally pulling out.

One official suggested that such a long withdrawal period might encourage the Soviets to believe they had won implicit acceptance of a right to delay a final pullout until they were certain a Soviet-style government would continue in Kabul.

"The minute we accede to the withdrawal period going beyond the logistically necessary time, we are playing Russian roulette," an official said. "We are then betting whether or not the Russians can entrench Afghan party leader Najibullah in power during whatever withdrawal period we agree to. If the Russians discover they guessed wrong and are unable to entrench Najib in Kabul, they will start reneging on their pullout."

Both Pakistani observers and the Afghan rebels' leadership reacted skeptically to Gorbachev's announcement that six regiments -- reportedly between 6,000 and 7,000 men -- would be withdrawn before the end of the year. An estimated 115,000 Soviet troops are in the country.

Resistance officials here and Pakistani political analysts in Islamabad said previous announcements of Soviet withdrawals had proven to refer only to rotations of Soviet forces, in which fresh units replaced withdrawn ones.

In Peshawar, one of the seven main party leaders of the resistance, Younis Khales of the Hezb-i-Islami said the announcement simply aimed to influence world opinion before the Geneva talks. In a statement to the resistance-linked Afghan Islamic Press agency, Khales said that past experience showed the Soviets "could replace the six regiments with 16 new ones."

Many rebels here in Quetta heard the news of Gorbachev's announcement in a Persian-language broadcast of the BBC, in which the announcer mistakenly reported a Soviet intent to pull out 70,000 -- rather than as many as 7,000 -- troops. "We knew even before he corrected himself that there must be some mistake," said Abdul Hafiz, a local official of one of the main resistance parties. "Nobody here thinks the Soviets really want to go home."