Jack Wilshere's goal four minutes from time was just enough for Arsenal to see off Swansea City 1-0 in an FA Cup third round replay at the Emirates Stadium on Wednesday.
Arsene Wenger's side had dominated the second half but a succession of chances that were either missed, blocked on the line or hit the woodwork meant the tie appeared destined to go into extra time.
But Wilshere, who was his side's man of the match, finally broke Swansea's stubborn resistance and the Gunners' reward is a trip to second-tier Brighton, who knocked out Newcastle, in the next round.
Wenger made three changes from the side that had lost 2-0 at home to Manchester City in the Premier League on Sunday.
Per Mertesacker replaced the suspended Laurent Koscielny in defence while Francis Coquelin and Olivier Giroud came in for Alex Oxlade-Chamberlain and Lukas Podolski further up the pitch.
Swansea made six changes from the side that had ground out a goalless draw at Everton at the weekend, the most notable of which was the choice of Danny Graham instead of top-scorer Michu up front.
Michu scored both goals in Swansea's 2-0 win at the Emirates on December 1 while Graham was the man whose late equaliser in the 2-2 draw at the Liberty Stadium earlier in the month had brought about this replay.
Theo Walcott, playing on the right instead of the central attacking role he favours, sent in an early cross that Giroud headed over and the France striker then fired another passable chance wide as the visitors began nervously.
Swansea's first chance fell to Nathan Dyer but Thomas Vermaelen made an excellent block, as did Kyle Bartley, the former Arsenal defender, at the other end when Abou Diaby unleashed a powerful drive.
And the Welsh side hit the bar in the 25th minute when Bartley rose to head Wayne Routledge's delivery past Wojciech Szczesny as the Arsenal defence failed to react.
Arsenal almost scored with the last kick of the half however when Chico Flores's attempt to head away a corner bounced off Mertesacker and straight to Thomas Vermaelen, but Swansea goalkeeper Michel Vorm blocked with his legs.
Arsenal came close with the first attack of the second period too, with Walcott out-pacing Flores -- who did appear to make contact with a hand.
The England forward stayed on his feet, however, and saw his chip elude Vorm but bounce wide of the far post.
The visitors' goal lived a charmed life as Vorm pulled off a fine parry to deny Wilshere and Walcott's volleyed follow-up was blocked on the line by Graham, with Arsenal's claims he had used an arm to do so ignored by referee Mark Clattenberg.
Within seconds Leon Britton headed off the line to deny the Gunners again and Walcott fired a good chance wide before Michu replaced Graham with just under 20 minutes remaining.
Giroud twice shot straight at Vorm -- the second was a really good opportunity -- and Swansea twice almost made him regret it, first when Szczesny had to tip a long-range effort from substitute Ki Sung-Yueng round a post and Flores sent a header into the side-netting from the corner.
Walcott again came close to settling the tie with a glancing header from Bacary Sagna's cross that bounced off a post.
Swansea were hanging on grimly and Dwight Tiendalli twice blocked on the line, first to keep out Mertesacker's header and then to clear Giroud's shot.
But the pressure eventually told when Wilshere finally beat Vorm with a well-struck shot from the edge of the box after Giroud had set him up.