Yugoslav Prime Minister Ante Markovic proposed Friday a 22.2 percent devalution of Yugoslavia's currency and limits on public spending and salaries for 1991, warning anew of disaster if the recalcitrant leaders of the republics continue undermining his Western-style reforms.

"Yugoslav society is at a crossroads and the next year is crucial. By unilateral actions and measures in the individual republics, the integrity of the country is endangered," Markovic said in presenting his economic plan for next year to Parliament in a nationally broadcast speech."If these processes continue, we will enter into chaos," he said, noting that Western nations view Yugoslavia's tangle of ethnic, political and economic tensions as one of the gravest sources of instability facing Europe.

Reaffirming views that the 65-year-old reformer is the only politician with the ability to lead Yugoslavia out of its deepest crisis since the 1945 communist takeover, the legislature's Chamber of Republics and Provinces voted to extend its own mandate, automatically renewing Markovic's 20-month-old tenure, which was to have expired Monday.

The extension will be effective until multiparty elections to the Parliament's Federal Chamber are held, probably by May. The six republics nominate members to the second house.

All six republics have now held their first multiparty elections since World War II, but the outcomes have further complicated the nation's problems, bringing nationalists to power in Slovenia, Croatia and two other republics and maintaining communist rule in Serbia and Montenegro.

Markovic urged that his 1991 plan be implemented until the resolution of a festering dispute over whether the federation of six republics be retained, as demanded by the largest, Serbia, or converted into a confederation of independent states, as sought by Slovenia and Croatia, which are threatening to secede.

Western experts expressed doubt whether Yugoslavia can be pulled out of its political and economic morass, which has helped fueled fears of disintegration into civil war or intervention by the Communist-led military.

"It is difficult to see how you can stitch back the threads of reform into a quilt, let alone into a whole piece of cloth," said a Western diplomat.

Inflation for next year was projected at 40 percent, compared to 130 percent this year and 2,600 percent in 1989.

Several republics are believed to be close to bankruptcy.