After slipping from the summit during the week, the Gunners overcame struggling Crystal Palace 2-0 on Sunday thanks to Alex Oxlade-Chamberlain's second-half brace.
Now the focus turns to Monday night when Manchester City, which is two points behind Arsenal, hosts Chelsea, which is three points further back in third.
"I will watch that game with interest because it's two competitors against us and it's always interesting to see how they behave," Arsenal manager Arsene Wenger said. "We gained some points through some other opponents like Liverpool and Man United over this weekend, and I think we know that our results at the Emirates will be massively important until the end."
Liverpool remained in fourth place, but its 1-1 draw at West Bromwich Albion was a missed opportunity to strengthen its pursuit of Champions League qualification.
Having led through Daniel Sturridge, Liverpool defender Kolo Toure sloppily gave the ball away to allow Victor Anicheb to equalize for West Brom.
Although Wenger still talks of United as a rival, an eighth loss of the title defence — at Stoke on Saturday — means the champions are seven points behind Liverpool.
And Arsenal is 15 points ahead of United in its quest for a first league title in a decade, after bouncing back from a hard-fought 2-2 draw at Southampton on Tuesday.
Despite dominating against Palace, Arsenal was frustrated throughout the first half in its pursuit of a goal against their relegation-threatened but well-organized London rivals.
The breakthrough came inside two minutes of the restart as Oxlade-Chamberlain scored his first Arsenal goal since December 2012 on his first league start since being injured on the opening day of this season in August.
Santi Cazorla weaved his way through the Palace defence and dinked the ball over for Oxlade-Chamberlain to lift the ball over goalkeeper Julian Speroni from close range.
And the 20-year-old England midfielder netted a second in the 73rd minute as he slotted seamlessly back into the injury-hit team.
Thomas Rosicky knocked the ball forward to Olivier Giroud, who backheeled it for Oxlade-Chamberlain to strike low into the net as Arsenal went a 10th game in all competitions unbeaten.
"It's something I want to add to my game — more goals — so it was nice to get two today," he said.
And this was a rare day when Luis Suarez couldn't score for Liverpool, instead turning provider at the Hawthorns.
In a disjointed first-half display by his team, the Uruguay striker fed the ball to Sturridge at the far post to poke the ball into the West Brom net in the 24th minute.
But the winning position was thrown away in the 67th when Toure's slack cross-field clearance went straight to Anichebe, who levelled with a low shot from a central position.
"Kolo probably shouldn't have received the ball under pressure, and a pass can be misplaced," Liverpool manager Brendan Rodgers said. "We look to build our game from behind and that has won us many games this season, our ability to construct the game from behind.
"Sometimes it will cost you. Today was unfortunately one of those days. Kolo Toure has been brilliant for me, a real leader and an outstanding professional and unfortunately it was that mistake, but there's no blame on him."
The draw pushed West Brom a point clear of the relegation zone, just above Palace on goal difference.