Luis Amarilla scored the only goal as Minnesota United sent St. Louis City crashing to their first defeat of the season in Major League Soccer on Saturday.

Amarilla stepped up to rifle home a 78th-minute penalty at St. Louis's Citypark stadium to ensure that Minnesota maintained their own unbeaten start to the campaign.

Paraguay international Amarilla had won the spot-kick moments earlier after darting into the penalty area and being brought down by a clumsy challenge from St. Louis's Canadian international Kyle Hiebert.

The defeat is the first blemish on expansion club St. Louis's impressive start to their debut MLS season.

Prior to Saturday, St. Louis had a 100 percent record, with five wins out of five to lead the Western Conference by five points.

"We knew we'd have to ride our luck a little bit at times and we did that on occasion in the first half," Minnesota head coach Adrian Heath said after his team's win.

"I thought we did that, and in the second half we were outstanding and far and away the better team," the former Everton forward said.

"Without the energy levels, and determination and enthusiasm to run around and defend the goal, none of this is possible."

Minnesota are fourth in the Western Conference standings, with 11 points from five matches.

Although St. Louis remain on top of the standings after Saturday's loss, their lead has now been trimmed to two points after the Seattle Sounders grabbed a 2-1 away victory over the Los Angeles Galaxy in California.

The Galaxy -- the most successful team in MLS history, with five championships in nine MLS Cup final appearances -- are still awaiting their first win of the season and are languishing in 12th place in the 14-team Western Conference.

Galaxy fans have staged a series of protests calling for the dismissal of club president Chris Klein during the opening weeks of the season, and boos rang out on Saturday after Brazilian winger Leo Chu's low strike fired Seattle into a 2-0 lead after 35 minutes.

US international Jordan Morris had given Seattle an early lead after 21 minutes, tucking away a low finish from close range after a sweeping counterattack sliced apart the Galaxy back four.

Jalen Neal pulled a goal back for Galaxy on 63 minutes, but Seattle held on to claim all three points.

In the Eastern Conference, Cincinnati have a one-point lead at the top of the table after a 1-0 win over Inter Miami.

Cincinnati are unbeaten after six games and are a point clear of Atlanta United.

Atlanta, thumped 6-1 by Columbus last week, bounced back from that loss with a 1-0 win over the visiting New York Red Bulls.

Atlanta welcomed back Argentina World Cup-winner Thiago Almada following the international window, and the South American had a hand in the game's only goal.

Almada's rasping long-range strike was fumbled by New York goalkeeper Carlos Coronel and Giorgos Giakoumakis was on hand to stab home the rebound.