The Consumer Product Safety Commission is considering allowing U.S. manufacturers to export to foreign markets millions of children's pajamas that have been banned in the United States because they contain the flame-retardant chemical Tris, which the commission found could cause kidney cancer.

Meanwhile, jobbers and exporters in New York's garment district have been advertising in trade journals, trying to buy up huge stores of Tris-treated children's garments at cut-rate prices in anticipation of a ruling by the federal government that they can be sold abroad.

The consumer product officials, already under intense criticism for mishandling the Tris ban in April, and causing severe financial hardships to most of the nation's small manufacturers of children's sleep-wear, suddenly has found itself between a rock and a hard place.

It can rule, in effect, that a fabric containing a cancer-causing substance is not suitable for use by American infants but is suitable for use by foreign babies.

Another option is to retreat from its controversial position that Tris has been found to cause cancer in laboratory mice, and therefore is dangerous to humans.

Still another option, presumbly equally unpalatable, would be to ban exports of the chemically treated material and inflict further hardship on the beleaguered sleepwear industry, which already has engaged the government in a series of lawsuits and claims for damages.

The commission is scheduled to meet in Washington Friday to hear arguments about the export proposal and make a decision. It will also consider other aspects of the Tris ban and hear testimony from manufacturers, union representatives and consumer and environmental groups.

Although Tris, a chemical developed by the fabric industry in response to a series of fatal accidents involving children wearing flammable nightgowns, has been banned here, most foreign nations have no such prohibitions.

Moreover, the federal Hazardous Substances Act, which provides $500 fines and 90-day prison terms for persons who market banned products do-hole that would permit export of Tris-treated fabric.

A section of the act specifies that a person will not be subject to federal penalties "if any hazardous substance is shipped or delivered for export to any foreign country in a package marked for export on the outside of the shipping container and . . . in accordance with the laws of the foreign country . . ."

The same legal clause, however, specifies that the forgiveness will not apply if the banned substance is offered for sale domestically.

Appearing at Friday's meeting will be representatives of the newly formed Independent Cutters and Sewers of Children's Sleepwear Association, which warned that scores of apparel firms face bankruptcy by being forced by the commission to repurchase Tris-treated garments from retailers.

However, Louis Bates, a founder of the association, said his group will take no position on the export proposal.

"Who are we to be judge and jury to the whole world?" asked Bates, a Greensboro, N.C., apparel manufacturer, in a telephone interview.

"My personal observation is that may not be considered good for this country, another country, may find perfectly acceptable, whether it be Canada, exico, Uganda or whatever. I'm not in a position to judge what is good for them," Bates said.

In April, the government banned further sale of Tris-treated children's garments because laboratory tests showed the chemical could cause a rare form of kidney cancer, particularly if infants chewed or sucked on the cloth.

At the time, trade sources estimated that there were 18 million size zero to 14 garments in commercial pipelines worth amost $200 million, not including purchased but unwashed material that could be returned by consumers under the federal order.

The apparel manufacturers, which the government ruled must shoulder the entire burden of repurchasing Tris-treated garments from retailers, reacted in a storm of protests, saying that the nation's $400 million children's sleepwear industry would be "annihilated."

U.S. District court Judge George Hart subsequently ruled in Washington that the commission had acted "arbitarily and capriciously" in the manner it imposed the ban, and ordered that all industries involved in the making of children's sleepwear - including chemical, fiber, textile and apparel - should share the cost of the recall protram.

The commission came under further attack when a federal judge in Greenville, S.C., moved last month to enjoin the federal government from enforcing its ban on Tris.

But apparel manufacturer sources noted that if Judge Robert F. Chapman overturns the Tris ban on the ground that Spring Mills, Inc., was denied due process, the federal product commission could simply reissue the ban and comply with due process requirements. This would prolong the dispute for months more, they said, without necessarily altering the outcome.

Against this backdrop, textile jobbers and commodity speculators recently began advertising in trade journals - primarily Women's Wear Daily - that they would purchase Tris-treated goods for export.

However, Bates, whose organizations represent nearly all the children's sleepwear firms, said nobody is selling.

"I don't know anybody who has sold their inventories to these guys. All the leeches come out of the woodwork when something like this happens, but nobody is selling," said Bates.

One manufacturer in Manhattan's So Ho district, Jesse Ganis, said today the jobbers "are looking for a ripoff in case the export is approved. They're offering $5 and $6 a dozen for goods worth $48 a dozen, but we're not selling."